Yesterday [16th]  was the last day of my data cycle and I had a few GB left so I downloaded some stuff I had held off downloading during the month for fear I would go over but I see this morning that my new data cap has had 1.5GB taken off it for data that was actually downloaded yesterday.
All downloading was done and dusted well before midnight but because of the slow meter update some usage was attributed to today and new usage cycle.

Seems a bit unfair.  I can understand a slow catch up on usage but I would at least expect it to be attributed to the correct day and data usage cycle.

So how long before the end of my last day of the cycle do I have to stop downloading in order to have it applied correctly?  I wouldn't want to download a 5-6GB file on the last evening and find out that the usage had all been taken off the new month's cap.

1.5GB isn't huge but it is most of a day's allowance and it is the principle. I paid for that usage last month but you have insisted I take it out of this months cap.

[1st world problems, I know]