Shruti, I had the same question a while ago and I went and asked a Goodreads friend who’s read count was in the thousands. This is what he had to say —
“Well, I read a lot of graphic novels which are very fast reads like 30–60 minutes tops. The novels are several hours and you’ll notice there are less of those.”
So, it also depends on the kind of books they tag as read.
I also read on Goodreads forum somewhere that they were planning to include magazines too in their catalog. So that would catapult the read numbers even higher.
I’ve only read a 112 books marked on Goodreads. I must have read about 130–150 in my lifetime. I’,m 30.
Having said all of that, you could probably friend me on Goodreads — https://www.goodreads.com/user/show/9807888-rajat