Some citrus will self cull excess fruit, but as long as the tree receives adequate water and fertilizer, it should support at least 10 lemons.

My dwarf Lisbon lemon is only slightly larger than yours, based on the picture, and it matured 14 full-sized lemons over the winter. I just picked and used the last one a few days ago. It definitely earned its keep this year.

I would except 10 to 14, thank you for the input.

Eric