please help me with this

I'm trying to enter a formula that gives me the results in the equation below.

25-17.45=7.55*10338=78053/21000.3=3.72

when I enter =if(c6-c7<=0,"0",c6-c7*10338/21000.3) I get 14.89

3.72 is the correct answer that I need.  My only cell references are in column C.

I've been doing the calculation on my phone and thought I could just add a column and put in the formula and have the answer right there.  (3.72 tells me I will need 3.72 hours to fill my water tank.)