Dishwasher draining through air gap?

It’s a brand new, just installed like three weeks ago dishwasher. Previous dishwasher was a POS and did the same thing. I figured the problem would solve itself when the new dishwasher would be put in. Can someone explain it to me like I’m a 2 year old distracted by a bug(I have a five month old so yeah). How do I fix it before I accidentally get water all over my counter(again). Sink and garbage disposal don’t seem clogged, and I have no idea what I’m looking at under the sink.