It definitely looks like a calamondin; a satsuma would be substantially larger. As for what you do with it.... mixed drinks? They are nice lemon substitutes.

Ya, I would save it!!! You only have one tree now, that’s not enough. This might be a reason to get serious in citrus. Looks to me a good beginning. What my advice: Buy more! It’s not a $15.00 mistake.

Usually Owari Satsumas are grafted. Frequently calamondin are rooted from cuttings. What is yours? Satsumas, when they have a good bearing year, tend to have smaller fruits. Off years, fruit are fewer but much larger. My Owaris are fairly sweet right now, so you def. don't have an Owari.

Even that said, your fruit look quite small -- more like a calamondin. I would be pretty ticked off, even though the price was not that much. I would never use a calamondin, but that's me. Calamondins might be a good citrus to learn with though, since they tend to be more tolerant of tougher conditions. Then, after you have mastered growing your calamondin, you can move on to sweeter varieties.

Regarding nursery stock in general a percentage of material gets mislabeled during production and shipping or has the wrong naming right from the start of the cycle, is sent to retailers as something other than what it is - that may be what happened in this case. Perhaps even the entire block of plants shipped as the kind you wanted were actually calamondins in this instance.

Or the grower is using calamondins as rootstock - if this is ever done - and the graft failed in the case of the specimen you bought, the stock replaced the scion and was grown on and shipped without it being noticed the finished specimen did not consist of the original grafted combination.

You may also have a kumquat