Numbers in [brackets]?

[FroBodine]

What do the numbers in brackets, e.g. [1] next to attack values mean? I cannot figure this out, and don't see anything in the manual. In fact, the manual is missing quite a bit of detail information like this.

Incredible game. I am having a complete blast so far, and I'm just on the 5th tutorial mission.

[VPaulus]

Someone asked the same question in the SLitherine forum:
Answered by a dev:

Unit cannot attack on voluntarily with an attack value in brackets.
A Stuka with [5] cannot attack a fighter, but it returns fire with that [5] when attacked.

[Dragoon.]

When in brackets a unit can retaliate against a certain unit type when attacked but is not able to launch an attack on it's own.
In most cases you will find that ground units have an air attack value in brackets. Usually only anti air units are able to initiate attacks against air crafts, but some ground units can fight back when attacked. If the value where zero it would posses no means to fight back and the attacker does not need to fear any causalities.

[FroBodine]

Thank you both. Yeah, it was me who posted in the Slitherine manual as well. I figured it's a useful question to ask, so both places can benefit from the answer.

Thanks again!