Synod of Dordt 1618

According to Mulsow & Rohls, 2005; there were 13 Remonstrants (also Labuschagne, 2019; Satama, 2009) out of a total 100 or so representatives.

From Mulsow & Rohls, 2005:

The internationally represented assembly was made up of 84 members, of which 61 were Dutch pastors, Church elders and professors, and 23 English, Scots, Germans, and Swiss. In addition 18 official representatives of the States General were present, the political commissioners with their secretary, Daniel Heinsius. Bogerman, on account of his hard-line Contra-Remonstrant stance, was elected to the position of Moderator of the Synod, and Hommius to the position of first secretary. The Synod decided to summon 13 Remonstrants from each of the provinces, with the exception of Utrecht, whose Provincial synod had sent three Remonstrants as official members to the Synod, who were henceforth given the choice either to give up defending the Arminian cause or the change to the side of those summoned. These latter were finally replaced by three Contra-Remonstrants. So far as the manner of handling the dispute between Remonstrants and Contra-Remonstrants was concerned, the Synod was effectively a tribunal whose aim was clear from the outset: the Remonstrants were to be convicted and their doctrines anathematised as heretical. This was already reflected in the seating order: the Remonstrants were to sit at a table which was positioned in the middle of the assembly room, whilst the Dutch and foreign delegates in charge of the prosecution under the direction of the Contra-Remonstrant Bogerman were to sit grouped around them. The Remonstrants, who were not even allowed to appoint their own representatives to the Synod, found themselves from the very beginning in the role of the accused after the Contra-Remonstrants had declared themselves as their judges[.]

You can see this intimidating seating arrangement in the Copperplate etching below. Someone, presumably Episcopius, stands at the head of the table, with what appears to be 6 delegates to his left, and 6 to his right.

Conclusion: Aspects of Questionable Fairness

There appear to be four main reasons to support the idea that the representation at the Synod was uneven and unfair again the Remonstrants:

1. The Remonstrants were outnumbered at least 9:1.
2. The Remonstrant delegates had no speaking or voting rights (Satama, 2009), and only had Episcopius as their spokesperson.
3. The Remonstrants were not allowed to appoint their own representatives (so their number was confined only the those summoned).
4. The Remonstrants were required to sit surrounded by the others in an intimidating and degrading fashion.

Appendix: 13 or 14 Remonstrants?

Wikipedia states 14 Remonstrants were present at the Synod, however it cites Mulsow & Rohls who give 13. So Wikipedia appears to be mistaken. I could not find any reliable sources independent from Wikipedia which state 14 rather than 13. In fact, that same Wikipedia article, citing Jacobus Regenboog's Historie der Remonstranten, 1774, gives the summoned individual's names, counting 13 in total.

The copperplate above appears to have 13 Remonstrants, although it's difficult to tell for sure at the image resolution.

This 17th Century Coin depicting the Synod appears to have 12 people at the centre, with a 13th walking away, but it's hard to make out. However it's some more evidence against the 14 number.

References

Labuschagne, Pieter H.J.. (2019). Lessons from the Synod of Dordrecht (1618-1619): A missional hermeneutic for the decolonisation and Africanisation of the curriculum. In die Skriflig , 53(3), p. 3. https://dx.doi.org/10.4102/ids.v53i3.2482

Mulsow, M., Rohls, J.. (2005) Socinianism and Arminianism: Antitrinitarians, Calvinists, and cultural exchange in seventeenth-century Europe, Brill's Studies in Intellectual History, Vol. 134, p. 38. https://books.google.com/books?id=E9qBWrLuLsYC&pg=PA38

Satama, M.. (2009) Aspects of Arminian Soteriology in Methodist-Lutheran Ecumenical Dialogues in 20th and 21st century, Master's Thesis from University of Helsinki, p. 14. https://helda.helsinki.fi/handle/10138/21669