yes. correct. its in the datasheet too
10X SCALABILITY WITH WIRELESS MULTI-NODE BRIDGING - Each root bridge capable of supporting up to 10 receiving bridges.
http://a030f85c1e25003d7609-b98377aee968aad08453374eb1df3398.r40.cf2.rackcdn.com/datasheets/ds-zonef...with internal antenna P300 got 30 degree beam width so to cover 360 degree you need to have 12 root P300 at the central point
another option is to go with P300 with 120 degree external antenna which will reduce no of devices at central point to just 3.
Above both options does NOT support 50 remote devices so you need to Talk to Ruckus SE in your region to help you design a better solution.