Time And Cost Calculations ..

I am compiling a simple worksheet that will keep an ongoing track of labour costs in a production environment. The objective is to end up with a labor cost "per unit" for packing punnets of soft fruit.

The source data I have is;

1 - Start time and end time of the job

2 - Any breaks taken during the job

3 - The number of staff it took to do it

4 - The status of the staff (Supervisor, temp, etc) and their hourly pay rates

5 - The number of punnets packed.

With all of the above it should be a relatively simple exercise to calculate the cost per unit (and with a calculator is!). My problem appears to be that I am not formatting something correctly, because when I try to calculate the costs for the employees' my costs are obviously wrong. I have attached my early draft for reference, in the example shown I am showing that a supervisor earning £7.50 an hour worked for 1 hour 15 mins at a cost of £0.39