Magnetized?

[Easy E]

I have a brand new watch, maybe 2-3 weeks old. I noticed it seemed to be a bit slow, so I measured it a couple of times and turns out it was 15 sec slow per day. Everything else seemed ok, so I just figured it needed to be regulated. Called the Mfg looking for an AD or SC near by and they just had me send it to them - they provided the box and label. They have had it just over a week and called me today and said it was just magnetized and is now running within spec. Suppose to ship back tomorrow.

I have always been under the impression that a magnetized movement will run faster, not slower. Are both possible? How does that work?