Hello, Peter.
I just installed a plugin "Card Statistics"
by bonoshi.
It shows the Next Interval right after you rate the card. I noticed those numbers 39 40 41 42 displayed by Plugin. But, ...
When I opened the Browser, the Next Interval, in all 4 instances, was 1 month. I don't believe you would allow a 25% rounding error.
I'd appreciate your explanation, as usually.
Meanwhile, I will let the author know, too.
Thanks.
Vit