Rach procedure how Group A and Group B selected?

Hi Experts.

How UE select Group A and Group B?
Group A is for small packet?
Small packet means what?
Group B is for large packets?
What is these means in real scenario?

Please answer this.

Message size for group A is sent to UE in SIB2. Typically 56 bits which is size of RRC connection request. So, if UE is going to send RRC connection request message or smaller will use group A. If message to be sent is larger, ue will use group B

If we are doing intial rach procedure then UE select group A or Group B?
In this how size is defined like for MT access ,MO Data, MO signaling?

Rach for rrc connection request (msg3 later) such as mo, mt data/signaling will use groupA 56bit.
Rach for handover complete in targetcell may use groupB > 56 bit.

Even for HO, group A is used ( unless path loss threshold is met)

So I say HO, groupB may be used.