The dispelling player gets a number of dispel dice equal to the top half of the roll of the Winds of Magic dice.
For example, if the Winds of Magic dice are rolled at and show a 1, 2, 2 and a 3, the casting player will get 8 power dice (the total of the 4 dice) and the dispelling player will get 5 dispel dice (the highest result of 2 dice). These dice are then placed in a dispel 'pool' in a similar manner to power dice. Each time a Wizard attempts a dispel, they take dice from the dispel pool to do so.