score:8
As outlined in the answer to For UK/USA bound flights, are details entered during online check-in, such as date of birth or passport number ever checked by airlines/immigration?, airlines don't care in the slightest about any fields you enter during reservation or check in other than your name. You can put in the wrong birthday, passport number, passport expiration date, etc, and you'll still be allowed on board, though sometimes online check-in might fail if you're traveling to a foreign country, and you'll have to check-in at the airline's departures desk.
So if I were you I'd not worry about it and show up for my flight as usual. No need to fix it, unless it's super easy to do in the booking management website.
Upvote:6
You can edit passenger details but they are likely going to charge for it "depending on your service level".
See Can I correct traveler details? (Kiwi.com)
Recommendation: If any possible, book with the airline directly. If an online travel agency (OTA) is substantially cheaper, use a reputable one. In my opinion, Kiwi is NOT reputable. I suggest reading reviews and form your own opinion.