It looks like this is important, your card can support 16MB of RAM total on it via the SIMMs,
maximum 8 MB is autoconfigured in the 16 MB address space, the exact amount is set by jumper (on the board)
the remaining memory is configured as extended memory by the FaaastROM driver
so i'm guessing either
a) the 8MB board is the 8 meg autoconfiged and the 8MB on your accelerator is being handled via the FaaastROM driver
b) the 8MB board is the 8 meg autoconfiged and the 8MB on your accelerator is being handled via the CPU slot's (24 or 32 i can't remember precisely) bit memory bus (the zorro II is 16bit which is why the 8mb autoconfig limitation is there) (the card your using is a later model of GVP board which may actually take advantage of the increased memory addressing in the CPU slot)
c) your a wizard harry!
BTW, great bit of info on the particular memory addresses is here! shows the 8MB chunk for fast ram, 2mb for chip, etc.
https://en.wikipedia.org/wiki/Amiga_Zorro_II
sorry for derailing the original thread!