For those who are having issues adding a monthly data usage limit that resets on the first, it seems to be an issue with it thinking 1 is 0, 2 is 1 and 3 is 2 etc. It seems like a bug that Microsoft needs to fix fast, or your can't add the 31st as a reset day.
Just a reminder, to set the 1st as the reset day off the month. Choose the 2nd
Lumia 920: Windows 10 Mobile Build 10512
Just a reminder, to set the 1st as the reset day off the month. Choose the 2nd
Lumia 920: Windows 10 Mobile Build 10512