Calculation not working

So I am struggling with the calculations in the Parts and Labor section. Previous version I had, worked calculation wise but i wasnt happy with the results. Original - where hours of labor is, it originally read Labor($). I changed it and want to input a calculation of the person putting hours of labor, ie 1, 2, or 3 hours worked and it will calculate the hours * 20.00. But I know I am overthinking and over complicating it. What am i doing wrong and how can I get it working the way i intended? (older version of .net framework as per instruction from professor) https://paste.mod.gg/arwsrwabktzk/0

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