1995 GMC Jimmy Model Year - Manual Difference

My GMC Jimmy has a VIN engine and model year code
of "W" however this vehicle has a Title and Purchase
Used always being known to be as a Model Year of 1995. (4.3 L V6 Vortek engiine )
This vehicle does have OBDII.
This vehicle has CPI specifically CMFI Fuel Injection.

Could you tell me why my Haynes Automotive Repair Manaul on page 0-5 designates my VIN :
1GKDT13W6S2547512 reads to be model year 1998 per manual?
Clarification is needed?

Thank you for the help