My question is about a simple multiplication of time by a rate. In a table "Syllabi" I have "Client hours total" in hours:mins worked & in Rate as a decimal to 2 places.

"Client hours total" is a simple calculation of elapsed time (end time minus start time). The calculation is -

(Syllabi::Rate*Client hrs total)/3600

So far I've not found the right script for the calculation. Dividing by 3600 produces the wrong result in calculation field "Amount Earned". Where am I going wrong I'd be grateful for help here .

Can you give us a few examples to verify?

The raw data, what your calc is getting and what you expect.