There is no much meaning in this version number value.
But this value is the same as ‘PTCH’ and ‘ROv#’ resource ID in System file (these resources are patches or overrides on some ROM routines).
For information only, here are original ROM version number of several machines:
• 105 for Mac 128 and 512 (64 KB size);
• 117 for Mac Plus (128 KB size);
• 630 for Mac SE (256 KB size);
• 630 for Mac Classic (512 KB size);
• 376 for Mac SE/30, II, IIx and IIcx (256 KB size);
• 890 for Mac Portable and PowerBook 100 (256 KB size);
• 1660 for Mac IIci, IIfx, IIsi, LC, LC II and Classic II (512 KB size);
• 1660 for Quadra 700, 900 and 950, PowerBook 140, 145, 160, 170 and 180, Duo 210 and 230, Mac IIvi and Mac IIvx (1 MB size);
• 1660 for PowerBook 520 and 540 (2 MB size);
• 1917 for Quadra 840AV (2 MB size);
• 1917 for PowerMac 6100/60, 6100/66, 7100/66, 7100/80 et 8100/80 (3 MB size — then 4 MB starting with System 7.5.1!).