Am I Doing Something Wrong?

I feel like I’m losing my mind here, and I really need an outside perspective. This might sound like a humble brag, but I promise I’m actually confused.

I’ve been working out at home for almost 2 years with just dumbbells. For biceps, I’ve been using 20s and 30s for about 6 months (before that I was only using 20s). Recently I started going to the gym and tried the bicep curl machine.

I’ve been pushing to failure on it, and I kept hitting 20 reps, so I’d rest, bump the weight up, and try again. Eventually I found a weight where I maxed out at 6 reps — 160 lbs.

That’s what’s throwing me off. I’ve never curled more than 30 lbs per hand, and now suddenly I’m apparently doing 80 lbs per arm? It feels like I must be doing something wrong or the machine is lying to me somehow.

Has anyone else had this happen? Is this just a machine thing or am I just somehow a lot stronger than I thought? Please help me make sense of this.

EDIT: Apparently, the machine is indeed lying to me. Thank you everyone for your replies. It helped me understand better what's going on. (Also, for reference, it was a seated bicep curl machine with pads behind the arm. I chose it because I got the full range of motion but with more shoulder protection.)