score:7
The 35 days are cumulative, but do be careful, because the day of arrival and day of departure both count as one day. With two trips to the Schengen area, that means there will be two of each, so a total of four partial days that must be counted as complete days against the 35-day allowance.
You must also leave the Schengen area on or before the "to" date of your visa's validity, regardless of how many days you've spent in the Schengen area.
A good source for this is Annex VII of the Schengen Visa Code, which says in part
4. ‘DURATION OF VISIT ... DAYS’ heading:
This heading indicates the number of days during which the visa holder may stay in the territory for which the visa is valid. This stay may be continuous or, depending on the number of days authorised, spread over several periods between the dates mentioned under 2, bearing in mind the number of entries authorised under 3.