brain regions from atlas "missing" in expression df

[elosse]

Hi, I noticed that my generated expression file contains fewer entries than the atlas I used, which I dont understand. More specifically I am using an atlas with 170 regions and the expression file contains 163 "rows" when it is done. As I understand it, this is not due to no expression values being assigned to those regions (and automatic discarding of them), since the expression file still contains two "rows" without assigned values (all NaN). The missing labels are at various places in the file (not all at the end or sth. like that). Is this an error on my part or is there an explanation for that? I am not sure if it is even a problem... Thank you in advance!