The number of unicast PTT messages that can be performed at the same time is a function of the recorded message lengths.     Here, we can see that in poor link conditions (DL -11 dB, UL -5 dB) we can achieve 0,4 exchanges / s of a 5s voice message. If we consider that messaging takes place in pairs, this means that if it takes an aggregated 10 seconds to record and listen to a message, then a minimum of 4 such pairs can be active at once at any time. Utilizing broadcasting functionality (SC-PTM)  one can obtain much higher scalability on the receiving end. Then a minimum of >4 groups of UEs can take part in a PTT session (assuming some tokenization of the “speaker”)