ADDENDUM: Explaining AmountRel, AmountFix and rowLength
In Blender the number you set to AmountRel & AmountFix is the number of intermediate animation points created when you click "Create". For instance, if you set the AmountRel & AmountFix each to 24, Blender will create 24 intermediate animation points (see picture below). If you set AmountRel & AmountFix to 32, Blender creates 32 intermediate animation points.
I assume the "Distance" number is the distance between the animation points.
In-game this does not seem to affect animation speed, but it does affect animation density. The picture below is of two fertilizer spreader patterns each using a different array file. The array with rowLength set to 24 creates a pattern that is slightly less dense. Note that the distance between the arcs is greater than the 32 pattern.