Please explain Maximum Expansion Distance

[Bogdanov89]

There is a setting called Maximum Expansion Distance in the enemy configuration during Map Generation.
Its description says "The maximum distance enemies will look to expand from other enemy bases" - however i am not understanding what this means.

If i change this between minimum and maximum (2 and 20) how will that affect enemy/insect expansions?
If i put it to minimum does that mean enemies will not expand if there is no room around their other bases?
If i put this to maximum does that mean enemies will sometimes travel far away from their other bases just to build a new base?
If i wanted a maximum challenge (most powerful enemies) should i set this to 2 or 20?

Thank you very much.

[Loewchen]

If you decrease it, enemies will expand closer to existing bases and vice versa.
If in the area you specify is no room for an expansion they wont create an expansion.
Yes.
The higher the value the faster the enemy will gain ground.

[Bogdanov89]

Thanks!

[Xeorm]

Maximum challenge I'd think would come from decreasing the distance. It'll more tightly pack them in, making them harder to root out.

[DaveMcW]

You always have the option to ignore tightly packed enemy bases. But you can't ignore a behemoth worm that expands just outside your turret range.

[Jap2.0]

I think there's something to be said for both high and low expansion distances (the former leads to more aggressive expansion, the latter to more dense expansion), but ultimately the frequency of expansion is probably going to have a far bigger impact on difficulty.