The theoretical limit of surface magnetism is half that of remanent magnetism.That is, if the remanence of N52 is 15000Gs, then the magnetic field is close to 7500Gs.
The limit is that the length of the magnet is much larger than the size of the pole side.
Moreover, the value of surface magnetism is only related to the ratio of length and diameter and remanence.
If you feel that the area is large, the surface magnetism is also large. That's because the size of the magnet must be much larger than the area of the Hall probe, otherwise the test value will be smaller or much smaller.