This is (another) bug that BuzzISR had found, and I am posting it on his behalf. Here are the bug's details;
The B-Mail counts how many letters left per message.
But, actually this number is wrong!
The number counts only the letters on a message, but actually the B-mail is limited by a smaller number.
I dare to say that I beiliev that it counts also the B-Mail subject, and that is the bug.