Cams for 318's

I have a 512 lift cam in my magnum
There Is only 20 thousandth clearance between the retainer and valve guide
Completely stock except for the cam and valve springs
Is that actual lift measured at the valve or what the cam card says? Not being smart, but if it's stated .512" lift on the cam, it's actually less than .500" due to pushrod deflection, valvetrain geometry etc.