A while ago, I noticed some very small oscillations in my Cloudflare R2 bill (1-2 cents / month) and decided to ask about it out of curiosity. Support was tepid - understandable for my $1 / month account - and it wasn't until later that I realized the difference probably had to do with the number of days in the month.
Would this API have helped?
Unless of course you're on their credits then miraculously they do support a hard cap with every service stopping the second you go one cent over.
Zeit is good. Glory to Zeit.