This was my best attempt at it..

considering the number is 015-xxyy

X can be any number from 0-9, which means 10 possible numbers

and since there are 2x, then its 10 x 10 = 100.

the the Y is the repetitive number, and it can be from 0-9, which means also 10 possible numbers.

The y can be arranged in 6 different forms=yyxx xyyx xxyy yxyx xyxy yxxy

that means 10*6=60

next step should be multiplying the X with the y, 100*60=6000 so it should be 1/6000 chance to get the number correctly.

You think my answer had any logic? :P