Calculating hours on Numbers

Hello,

This is the first time I am trying to use the "numbers" application to automatically calculate the number of hours my childcare assistant needs to work, and the least that can be said is that I am STRUGGLING; I've been at it for 3 hours and I still can't get it right.

I have one cell for the start of work and another for the end of work.

For example, I put 09:00:00 in the first cell and 18:00:00 in the second cell, and I would like Numbers to calculate directly 9h00 in a third cell.

Already, when I enter the hours, Numbers automatically adds today's date (I can only see it when I double-click on the cell, even though in "cell", in "data format" I set it to "none" for the date. I don't know if this has any impact, but I prefer to mention it just in case).

Then, I certainly am not using the correct formula or using it properly.

I tried the HOUR formula by clicking on the first and second cells (HOUR B1+C1). When I validate, it gives me an error saying "the arguments of the formula can only contain one date value".

What is the correct formula to use? What did I do wrong?

I hope I was clear enough in my explanations...

Thank you to those (or that one person) who I hope will take the time to respond....