So i tested it multiple times, steam machine self-buff don't work as description(and logic) says.
Since ability is cumulative every buff should add 5 damage and remove 1 each turn. Instead it removes only 1 from last buff.
How it works:chages -- stats on your turn -> stats on opponent's turn (changes)
1charge 5|6 -> 4|6 (4)
2charges 9|6 -> 8|6 (4+4)
3charges 13|6 -> 12|6 (4+4+4)
4charges 17|6 -> 16|6 (4+4+4+4)
etc...How it should:1charge 5|6 -> 4|6 (4)
2charges 9|6 -> 7|6 (3+4)
3charges 12|6 -> 9|6 (2+3+4)
4charges 13|6 -> 10|6 (1+2+3+4)
etc...Hope it helps.
peace