...edit: Now that I think about it the distribution happened for whatever credits I had up until October 1st (instead of October 7th). It makes perfect sense that way, because indeed in the meanwhile I had produced around 20,000 more foldingcoins (which are not yet credited because they will be credited next month). Is that correct?
Yes, that is correct.
Distributions run on a monthly cycle (usually on the 1st weekend of each month as payment for the prior month). Anything after that goes towards the next month to come.