Dual meaning of "good, if not great"

Example sentence: Alice is a good, if not great, dancer.

I notice people interpret this sentence in two ways:

1. Alice is a good dancer, but she’s not great.
2. Alice is a good dance. Actually, that’s an understatement, she’s a great dancer.

The first interpretation is my first reaction, but the second one is plausible as well. Is context the only way to distinguish between these two interpretations? For my purposes quite often there is no context available however. I am looking for help with how to interpret this expression in these situations.