The A500 with 68000 CPU supports a maximum of 10Mb RAM.
68000 can address 16MB memory. Depending on the system implementation, all or only part of that can be RAM.
68000 Amiga system memory map:
000000-1fffff chip memory (max 2MB)
200000-bfffff fast memory (max 8MB)
a00000-beffff reserved
bfd000-bfdfff cia-b
bfe001-bfefff cia-a
c00000-dbffff ranger fast memory
dc0000-dcffff real time clock
dff000-dfffff custom register
e00000-e7ffff reserved
e80000-e8ffff auto-config space
e90000-efffff secondary auto-config space
f00000-f7ffff 512KB ROM, total 1MB (cdtv, cd32)
f80000-fbffff 256KB ROM, total 512KB (KS 2.x, 3.x)
fc0000-ffffff 256KB ROM (KS 0.x, 1.x)
In theory it's possible to have 2MB chip, 8MB fast and 1792KB ranger memory, total 12032KB (though it is not trivial to hack both 2MB chip and 1.5+MB ranger). With some extra hacking it might be possible to put some memory into reserved areas like 512K to e00000, and second 512K to f00000.