Again a time question...HH:MM:SS or not

[trolle]

I have a report that gives me hours per individual in an HH:MM format.

I wish to work with time in decimal format. I know how to convert the HH:MM cell into a decimal format.

My question is:
Some cells in my report have HH:MM time and others have HH:MM:SS which does not allow me to convert into a decimal easily. Can I change the HH:MM:SS into HH:MM to continue with my work?

Very confusing, so I have attached a simple example.