Prometheus increase not handling process restarts

I am trying to figure out the behavior of Prometheus' increase() querying function with process restarts.

When there is a process restart within a 2m interval and I query:

sum(increase(my_metric_total[2m])) 

I get a value less than expected.

For example, in a simple experiment I mock:

• 3 lcm_restarts
• 1 process restart
• 2 lcm_restarts

All within a 2 minute interval.

Upon querying:

sum(increase(lcm_restarts[2m])) 

I receive a value of ~4.5 when I am expecting 5.

lcm_restarts graph

sum(increase(lcm_restarts[2m])) result

Could someone please explain?