A level Paper 2 Physics Help, 2019 Q2.1 AQA

I've genuinely never in my life been more confused?? I can't link the diagram but its on PMT, "When the apparatus is assembled with the switch open, the reading on the electronic balance is set to 0.000 g. This reading changes to a positive value when the switch is closed." So apparently this means, due to Newtons 3rd Law, that the Force of the magnetic field is upwards.
The wire is not connected to the Magnet or Yolk at all, its clamped and suspended. So if the Force pushes the wire up, and then there is a resultant force downwards (Newtons 3rd Law) then how on earth does the Yolk/Magnet "know" or experience this resultant force? Especially considering we know that the upwards force, from the field, that the wire experiences has no affect on the Yolk/Magnet, but somehow the resultant force does?? It just makes no sense