There are only 8MB-Original Sony-MCs.
I have yet to see a real original Sony-MC (not only looking like one), with more than that... It's physically impossible on those real original MCs, to have more than those 8MB, because the physical storage-size of the integrated chip isn't higher (except, if they would use newer 'chips' with higher storage-capacity...).
If you would use a logical 16MB-Partition on a physical 8MB-Chip, it would start writing either from the beginning or from the end, when you reached the max. physical storage.
Your Sony-looking MC simply isn't an original Sony-MC.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux