By round 4 of combat, this single unit already has 40 hits (!).
While it does have 4 attacks per round, these are mostly coming from counter-attacks - the lower part of the screenshots is details of just the second round of combat. As it's alone, and sturdy enough for this case, it's being attacked by every single enemy sub-units, and counter-attacks in return.
That's a lot of free actions for one unit...



