How to get time division data when data reset to 0

Hi Guys,
I using Grafana and influxdb to collect ‘product data’ in the assembly line. I make a chat by grafana to show how many products was done in every hour.

It works good, but i have one problem, sometimes the worker will clear the total count because of shifts change. this cause the division data less than 0.
image

Considering this serial data(each data 10 minutes):
100 200 300 400 0 10 20
the correct time division in this hour should be (400-100) + (20-0) = 320

I tried also search but no help, do you have any ideas? (Sperate to 2 time divisions when data set to 0 is also OK , in this sample, we can get two bars with 300 and 20)

Thanks a lot!