Changing time

Hiyas Peoples:
I have tried and just don't seem to be able to get the formula right here to change the time for the result. The result is the adjusted time which shows up as #######. I took other stabs at it but get times that are way off. I just want to subtract in this case 13.43 minutes from 12:00. In the example I have tried 1700/126.6 which equals 13.43 minutes. Now I want to subtract that from the time of 12:00. To get the adjusted time. The time, over amount and #in racks can change. I have a simple version working but want to make it even easier to use for some of the people at work that I should say steer away from trying to do anything on the computer. It's for a product change at work. That will keep inventory as close to the same level from start to finish.
I have made up another sheet to use for how long to leave the line down before starting it up again and have things within a minute of lost production. That one works great.


Color Change Time Adjustment Calculator

Time Over Amount Bulbs per min.
12:00 1700 126.6
#In Racks Time To Subtract
10000 13
Adjusted Time
#########
Any way to get the adjusted time to equal 11:47? For time and adjusted time it doesn't seem to make a difference. I can't get that number without either #### or a wrong time.
Any help would be welcomed.
Thanks
Zig

Try...

="12:00"-((1700/126.6)/1440)

...and format the cell as 'Time'.

Hope this helps!