Double 0 , 0 or triple 0

This afternoon I made an address list for my grandad on excel so that i could print it out and he could use it rather than the one he wrote in his shaky handwriting.

There was one number we came across - 25100032.

And he read it out to me as "two, five, one, double zero, zero, three, two."
Suren: "You mean 'triple zero' right?
Grandad: "No ... i mean double zero, zero."
Suren: "But thats triple zero."
Grandad: "No ... its against the rules."
Suren: "There are rules for naming numbers? ....."
Grandad: "Just write the number."