I found a nice paragraph explaining how many points are needed to earn the MACH title:
'There is one other agility title, MACh. - Master Agility Champion. The title goes in front of the dog's name. Once a dog is in the Excellent "B" class, it can start earning points toward the MACh. title. The dog needs to earn 750 points and 20 "double Q's". This is, twenty trials where your dog qualifies in both the Standard and Jumpers class.'