DP's showdown only 300+ to Shadowstalker?

In my last pvp match, opponent had Shadowstalker as its last ark & I had Don Penguini.

Did showdon twice & hardly did any damage. Is it supposed to be that way or it’s a bug?

Don’s showdown damage also depends on the number of Arks in the opponent’s lineup. If there is only one Ark, showdown does much less damage.