The FT2D memory space is a block of memory channels from 1 to 900, a block of "skip search" memories from 901 to 999, and a block of PMS memory channels in 50 sets from L1/U1 to L50/U50. Both "sides" of the radio, side A and side B, can access any channel stored in the memory space. There is no such thing as A memories and B memories.
There are 24 memory banks. Any memory channel (channels 1 to 900) can be assigned to any of the memory banks up to 100 memories per bank.
Page 54 in the Operating Manual talks about how the memories are arranged.