Your right Prior, the ready reserve (aka airport/standby) must commence once the brake is set. But I think, if you block in early crew tracking has no way of knowing this. So you might have a small gap from your adjusted block in, to the start of your RRSV period. If they are showing a gap on your schedule before you fly that round trip, I would call them and let them know that you must be on ready immediately after your scheduled block in. Or you must commence your rest period.