When using a custom day based period in custom mode, the values calculated will be incorrect for the day UNLESS you happen to include a month based period as well somewhere else. This is hard to explain, but the pictures hopefully will show the issue:
So as you can see from these images, the custom day feature is completely broken unless you happen to include a month based period. Then it magically fixes itself and starts working. I’m almost positive this is a bug, but maybe there’s something I’m missing here?