Yes, it's safe.
Deanna

Yes, I concurr with Deanna. Concentrating things INCREASES their keeping qualities, by decreasing the amount of water and conentrating the sugars, acids, and salts. Honey is a prime example of this -- it must be dried out to a maximum water content of 19%, otherwise, there is too much free moisture and microbes can grow. This is why bees work so hard drying out the nectar by fanning the hive during the gathering season.

Hooray - at all that work for 2 little cups will be worth it months from now!

Thanks!

Because citrus seems to take longer to set, you may find it will be quite firm in a month or two. I can't ever bring myself to making small batches of anything, unless the item is very perishable. Making a cup or two of jam isn't what I would want to bother making, unless it was just for a test.