It's really just mineral oil, with a little lemon scent added.
"Real" lemon oil - usually sold as Oil of Lemons - is highly corrosive.
What you have is fine (for a rosewood fingerboard; a maple board doesn't need anything) although a cheap bottle of drugstore mineral oil would be as good. Use it very sparingly - maybe once a year - and polish off as much as you can.
I bought that stuff because I was going through a lot of paper towels applying miner oil/lemon oil from a regular bottle
It's good stuff to use on unfinished wood. Apply generously, let it soak in a while, and wipe off the excess. On rosewood fretboards I sometimes buff a little too, because it makes the grain swell a little and leaves a bit of a sticky film.