You can write this: With double defensive power, if the fist defender in the trench wins, then it's attacking power is equal to the power remaining after the double defense or it's original power, whichever one's lower.

Not a kata issue. Closing.

Look, we can be sure that the "remaining defending power" of d is 4-2=2. The rule about "more points than usual" means that if it was greater than d's usual power (2), we would need to bring it down to 2 before attacking. In this case, it's not greater, so the remaining power stays unchanged and the rule doesn't really change the outcome. Similarly, if sss were attacking, the remaining power of d would stay at 1. That rule makes a difference in cases like attack from a single s. The "remaining defending power" of d would be 4-1=3, but the attacking potential of d is limited at 2.

Any ideas about how I can shortly express this in the description?

The code seems to have some problem.
My solution runs on other compilers but here it returns the wrong answer. What should I do?

I have a question
What happens when attackers enter the trench and get defeated?

suppose the attack is:

"ss "

"--|dzp|"

as d is 2 but also the first one in the trench it's defending power becomes 4 successfully defending.
but now what?
what will be it's attacking power?
will it be (4 - 2) or (2 - 2), as you've said "it's not allowed to use more points than usual."?