Circuit Breaker Finder - Finding TWO Breakers for one outlet
The Klein circuit breaker finder is just a re-branded High-Tech, the Harbor Freight brand for about triple the price.  

https://toolguyd.com/klein-breaker-finder-and-hi-tech-circuit-detective-identical/ 



So don't expect much.  But even with a good one, a breaker finder should never be treated as more than a guess to narrow down further testing and verification.  

If the breaker finder indicates two circuits, it's possible the wiring is crossed up somewhere and both breakers energize this receptacle.  That's not uncommon if someone makes a mistake connecting blacks to blacks somewhere.  However it's even more common for the breaker finder to make a mistake.  

If you turn off the breaker and test the receptacle for voltage, and find no voltage present, then you have demonstrated that that breaker and only that breaker provides power to that receptacle.  However:  In a case like this where you're concerned something's wrong, I'd not trust a non-contact voltage tester or a plug in receptacle tester to verify there's no voltage present;  I'd want to test with a good voltage tester or meter.