Reports indicate it was a muted response to indicate an intention to deescalate. They had to do something but they didn't go crazy. We'll see, I guess.
Same thing when trump assassinated soleimani. They rattle a saber a little bit and call it even. Trump announced a ceasefire agreement 3 hours ago so it looks like business as usual.
Evidently it's an imaginary ceasefire agreement and nobody even asked Iran, so... We'll see. The token retaliation suggests they aren't trying to escalate with the US specifically.