welcome to the forum. try this array formula:
=SUM(IF(Sheet1!$B$19:$B$200=B4,SIGN(Sheet1!$F$19:$F$200-Sheet1!$L$19:$L$197)))
...confirmed by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. You will know the array is active when you see curly braces { } appear around your formula. If you do not CTRL+SHIFT+ENTER you will get an error or a clearly incorrect answer. Press F2 on that cell and try again.
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