What do they mean

Simple. It ran in the old Super Stock class, "J superstock." The numeral is the owners race number. You can download older NHRA rule books back in the years to see what the rules were and how they changed over the years

Some classes might have an "A" after the designator "J" to indicate "Automatic" transmission

It would help if you knew what time period it last ran, as the rules "then" are not the same "now"