[Hitman]

Yes it is a percentage as far as I have seen and serves to indicate how far from one side the selection of the image must beging. The four numbers are IIRC LEFT, RIGHT, TOP, BOTTOM or the same but in another order. The first one is for sure "left".

For example: Crop=0,0,1,1 would mean:

Start from the absolute left
Start from the absolute bottom
Cover till the absolute right
Cover till the absolute top

Meaning select the whole image.

If you wanted to select only the central part of it, for example you would put: Crop=0.25,0.75,0.25,0.75

And that would mean:

Start from 25% of the whole image the left margin
Start from 25% of the whole image the bottom margin
Cover sideways till 75% of the image, where you will put the right margin
Cover upwards till 75% of the image, where you will put the top margin

This is more or less how I understand it, probably someone else will be able to clarify it much better. These numbers seem to have served for the purpose of allowing easily higher resolutions. Any image defined in the menu.ini with Crop you can drop and image of any size and the game will pick it because it is a percentage of it. The game will then resize it to fit in the part of the screen reserved for it, but bigger images will have excellent readability when they are big.