Best to post a photo of the pot wiring before doing anything. Looking down on the back of the pot, with the three tabs facing you, the grounded tab should be on the right, the output wire on the middle tab and the input wire from the pickup selector switch on the left-handed tab. 10 should give zero resistance between the input (left) and output (centre) tabs.

10 on the tone pot should give maximum resistance. When the knob is at 0, there is no resistance so the signal is directly connected to the tone cap for maximum treble roll-off. At 10, there's 500k resistance between the signal and the tone cap, so almost none of the signal passes to the tone cap, so you get maximum brightness.