Slitherine

Why do some troops have split combat stats when you scroll over them in the "purchase field", yet when you click on them and move the mouse away the stats are slightly different?

For example: British Infantry '41
Have 9 9 in the "Attack against Mechanised" when I have the mouse scrolled over the unit, but, when I move the mouse the field down below then changes the 5-9 Attack against mechanized units.

Second question based on the first... as the attack against mechanized is 5-9, does that mean that when he attacks his attack score will be as low as 5, and as high as a 9 on some randomized "die-roll"?

It has to do with terrain. Stay tuned, I'll post some more in a few minutes.

So, as you say, British Infantry 1941 shows attack strength 9 when you are focused only on that unit (click each image):
I figure they do this so that when you hover over another unit, the comparison of the two units is enabled by displaying the single numbers of each unit, side-by-side:
But now to your question, which is what the heck are these hyphened numbers that you see in that box when you move your mouse away and the unit is still in focus?
If you ever played Panzer Corps, this is similar to their concept of "close terrain." The first number, "5," is the attack value against mechanised (armored) units in OPEN terrain. OOB calls it "0% cover." The second number, "9," is the attack value against mechanised units in "100% cover," hexes like cities, jungles, forests, and hills. So 5-9 is the low-high range of the infantry's attack strength depending on the "cover rating" of the hex that the mechanised unit is standing on. It's supposed to replicate the effect that, in open terrain, infantry is much weaker against tanks but in cities, forests, and such, tanks cannot maneuver too well, perhaps cannot even rotate turrets sufficiently, and therefore are more susceptible to close infantry attack.

That's the best that I can put it. Here is the pertinent section from the manual: