I think my first ride ever was maybe a mile.
My first recorded ride was 4 miles and that took me near 30 minutes to do. lol - That was with stopping and taking a break. I would love to be able to ride as long as you can. But I just get so butt sore and wore out.
I am still a noob around here - but I think the general suggestion is not to worry about it to much. Push yourself just enough to do a bit extra every day. But at the same time don't burn yourself out to fast - I know I am in the same boat and just got off taking to many days off cause I was pushing it to much.
Have fun riding and welcome to these forums.