I've watched the install video for the Diono and the lady said movement of less than 1" side-to-side and front and back at the seatbelt/strap down point is a good install. If I move the carseat at the seat belt/stap down part of the car, the carseat is good. However, there's quite the range of movement if I grab the backside of the car seat and wiggle it side to side; and if I push the car seat from the back of its seat, it moves also. Is this right? If not, what am I doing wrong?

I'm installing it rear-facing.