Script math is causing 4% underextrusion

[The--Captain]

After having difficulty with the structure of this test remaining cohesive, I ran the numbers on the extrusion volume, and the script is underextruding by 4%, at least when using the default of a .2 layer height and a .4 line width.

I see a lot of lines like this:

G1 F3600 X-10 E0.31930

(extrude 0.3193 mm of filament over 10mm of X or Y movement)

.2mm (layer height) x .4mm (line width) x 10mm (movement length) = .8mm^3 required extrusion volume

However, .8mm^3 / ( 1.75mm(filament diameter) / 2 ) ^ 2 * Pi = 0.3326mm, not 0.3193mm.

This is a difference of 4%, which is significant, and perhaps significant enough to cause the failing structural cohesion I am seeing in the test. Knowing this, one can fudge the extrusion multiplier to make it work, but it would probably be better if it was just fixed outright.