I’m late replying to this, but I’m 99% sure the last 2 numbers are the year of manufacture. I don’t know if the first 2 numbers are the week of that year or what exactly. I would imagine it was for warranty purposes or something similar. I had several over the years when they were in production and the 90 or whatever the last 2 numbers were was either the year I purchased it or maybe say it said 90 and I bought it early in 91, it would still be fairly recent. I have some older models from the early 80s that have 8 whatever at the end.
Side note- when I was younger, I’d pull that tag off because I didn't like the look of it even though I couldn’t see it when the light was on the dash. I’m sure others took theirs off, too.