Can I retroactively add time to a counter?

[NoxEther]

Hi everyone,

I track the time I spend exercising with the Simple Counter function. I know I can right-click and add time manually to the counter on the very same day, but how can I add time to the counter for past days in order to have an accurate graph?

I am not a techie person and English is my 2nd language, so thank you for your understanding in case the solution was very obvious.