Your donated CPU time can be found on the "Profile" screen in the app.
Some users might notice that even if they haven't used their PC for 8 hours, HEWMEN Cell only shows 2.8 hours of donated time.
So, why doesn't it show a full 8 hours?
Donated CPU time is calculated using the amount of time your computer spends actually processing tasks. This doesn't include time when Cell is fetching new tasks or reporting results.
Your settings may be affecting this as well. If, for example, your PC is processing data for 10 hours and you have set your settings to use 10% CPU time as shown in the image below, then that registers as 1 hour of donated time.
More information on HEWMEN Cell settings are available HERE.