Babystyle Oyster 2: What are the two studs at the top of the pushchair seat unit for?

I've noticed that there are 2 stud buttons at the top of the pushchair seat unit (right at the top of headrest, on the inside where the hood starts). I cannot figure out what they are for as the padded insert doesn't have any corresponding buttons to secure it to.

Have you got any idea what they are for???

Thanks 😊