Hi,
Different groups do not have to mean that it is a different atom, they can also mean a different branching carbon chain. This can get tricky with fused rings like this, because you might have to trace a bit down the chain to see the difference between groups.
https://ibb.co/fM8PhXq I've shown the logic all out here, usually for steroids like this ring junctions (places where the rings meet each other) tend to be chiral centres.
Another way I like to approach this question is through elimination - you can draw this molecule out and cross off anything that is attached to 2 Hs or is not sp3 hybridized.
Please let me know if you need clarification.