The first number refers to the "class" of boat. 6=600 series, 7=700 series, 8=800 series etc. The higher the first number the "better" class boat. 6 and 7 series were basic entry level bass boats. 8 series were more of a tournament boat and the 9 series were the top end tournament boats. The 482 was a pleasure/ski type boat 18'2" long.
The second and third numbers were associated with the length. An 896 was an 800 series boat and the 96 meant it was 19'6", 901 was a 900 series 20'1" long. At least that's the way I remember it being explained to me when I bought my boat.
Gene