For an L3 charger, 20 minutes is a lot. If you are 20%, it should get you to 70% or so, it takes longer to go from 70 to 100% given how battery charging works.
Indeed! I literally just charged a long range model y at a 250kw Supercharger from ~20% to ~80% in 17 minutes (per Teslascope) this morning after towing a ride on trencher back to the rental shop. Was done before I had finished using the rest room and getting a coffee at the grocery store.
Ya, I think people really underestimate how fast L3 charging is, especially for cars running on empty. But not all grocery stores have L3 chargers, and they can get really busy in holiday weekends. I plan my trips around these, but I wish they had more capacity.