Certified GKH Gardening Expert
I compared the fruit and leaves to lemon tree images and I do not think it is a lemon tree. You have so many different kinds of fruits that grow in Florida, I suggest contacting your local extension director and asking what is popular in your area and showing him/her this photo. If you think it grew on its own, look around your neighborhood for a similar tree that may be the parent. It is also possible the tree was grafted and the desirable top of the tree died and the rootstalk survived and took over. They are usually less desirable fruit. You also could contact the seller and ask about it.