why nios occupy much more M9K blocks than its on-chip memory size?

i figure out these questions:

1.

in the digital binary system, the 5120*32bit occupy the same resourses as 9182*32bit. so in order to use the M9K more efficiently, i should change the On-Chip Ram size from 5120*32 to 4096*32.

i test this method on my project, and i works.

2.

the "jtag_uart_0_scfifo_r" and the "jtag_uart_0_scfifo_w" only have 512 bits, but each of them occupy 1 M9k, so i enlarge the JTAG UART fifo buffer depth from 64 to 1152, so the system gets more JTAG UART fifo buffer depth without cost more M9ks.