Turn the numbers on a cam card into the four valve events, overlap and advance. Then send the intake-closing point straight to the compression calculator.
A negative result simply means the event happens on the other side of the dead center, for example the exhaust closing before top dead center. Overlap figures at 0.050 in are much smaller than at seat timing, and small or negative 0.050 overlap is normal.
Advance is the lobe separation angle minus the intake centerline. Installing a cam advanced moves all the events earlier, which generally shifts power down the rpm range and closes the intake earlier, raising dynamic compression. When you degree a cam, the intake centerline is the number you check with a degree wheel and dial indicator.
Of the four events, intake closing has the biggest effect on cylinder pressure, which is why the compression calculator asks for it. Use the button to carry it over.