If you stack images, Siril reports different values for EXPTIME and LIVETIME. The EXPTIME seems to be the length of the sub. The LIVETIME is the total exposure time.
AAVSO is pulling the EXPTIME and using it as if it were the total time. I really don’t know who is right here. I’ve found sites that (somewhat ambiguously) support both interpretations.
I’m just wondering if someone can authoritatively say Siril is correct. If so, I guess I would have to get AAVSO to change (which will be difficult).