OK now I do better understand and this does answer my initial concern.
Taking the "Figure 10:Scaling the DRTLS showing anchor’s seat numbers ", and with your explanation, I do now better understand.
Could you tell me if the following assertions are correct:
Taking as correct that the transmission circles in the figure show the exact limit of communication between two. anchors.
The Initiator A only sees slots occupied by A,B,F,E. A sees over slots as unoccupied.
The Anchor B only sees slots occupied by A,B,C,E,F,G . B sees over slots as unoccupied.
The anchor F only sees slots occupied by A,B,C, E, F, G, I, J, K. F sees over slots as unoccupied.
The Anchor J only sees slots occupied by E,F,G, I,J,K, M,N,O. J sees over slots as unoccupied,
Depending on the algorithm, boot time, … I imagine that N could have taken the slot of A,B,C because from its point of view it sees the slot as free, and all its neighbours (I,J,K … also), so it can be allowed to emit on this slot…
This explains why the network can be extended to infinite number of Anchors (save other limitations 
).
Thanks in advance to your.