What exactly are you doing in this second pass? Why make this calculation?Second Pass
How big is your file? Right-click your file, choose 'properties' have a look and see how many bytes it is. Copy that number and get a calculator (or open up calc in windows) and do this calculation:
(your file size in bytes * 0.7) / 1024
[your file size in bytes times 0.7 divided by 1024]
This is how big the video part of your amv should be and be almost always certain to look very good.
And also when you IVTC, does it transform the FPS technically to 24 or 23.976?