Forward facing with harness only or lab belt ok too?

Mmmk we are so confused. Went to Target to get a second seat for hubby’s car to make things easier. We already have a 4ever in my car. We switched to forward facing recently due to her bad motion sickness. It has been so much better. She is a big strong girl- 4t clothes, 38” 33 lbs.

We picked out the Chicco 2in1 lap belt booster (it read 30lbs and 38” on the display) but then when I got home to research online it says harness only front seats should be used until 40-65 lbs. Wondering why this lap seat was advertised for 30 lbs and 38”? It is a latch down.

Here is a pic for reference. I might take it back for the Graco tranzitions 3in1 but honestly she

already hates wearing her harness in the 4ever.