Hotspot data shows 900 MB blocks of data -- which are estimates by ATT and do not reflect actual usage

My computer tracks the amount of data used on a connection. Looking at ATT's hotspot usage for my account online shows MULTIPLE 900 MB blocks (exactly 900 MB -- which shows it is not a real tracking of actual data used since to get to exactly 900 MB on 50 different occasions would be impossible). 

Why is ATT estimating usage? I pay for hotspot data and would like it to reflect accurately. However, the hotspot usage reported by ATT is almost double the actual usage that is recorded by my computer. No other devices are connected to my hotspot, so it is not an error on my end or someone tapping into my hotspot -- this is an error in the way ATT is estimating (which it shouldn't be doing) hotspot data.

This 900 MB issue has been posted about several times, and ATT constantly tries to state there is nothing they can do on their end, but this is strictly an ATT issue.

Please stop estimating data usage and remove the estimates from my usage.