Greetings,
I have a request. Rather than calculating the break taken by each employee, why don't you consider the productive time spent at work? It might sound the same thing, however the impact is entirely different.
Suppose you fix 8.5hrs a day x 5 days a week = 42.5 hrs a week
When you calculate the productive hours spent at work, it would be far more easier to keep a time-track. This way the employees would be focussed on meeting the required hours to claim a productive week. Beyond that if they take any break or even time-off, it will no longer require supervision.
Further more it would be easier for the managers , as they can allocate work based on the productive hours . There are several time tracking softwares that you can implement based on the operations that you have in your firm