Overall it looks pretty nice, the deltoid inserts into the brachialis, and in your sketch, it looks a little bit too far to the left on the model's left side. The thing you circled I think could be considered still part of the abs but the main divot is caused by the xiphoid process from the ribcage.

Those are abs and the deltoid placement on the right is correct because it inserts between the tricep and the bicep, basically above the brachiialis, the insertion on the left is a bit too much toward the outside, think of an S curve converging in on that part of the arm that’s right next to the shadow of the tricep.