Hi Raman.
The calculation of M should be modulo the number you're trying to factor  ie 10^25 N = (10^50+1) mod cofactor. But as xilman pointed out you just fill in the numerator and denominator in the Y0 and Y1 fields.
The idea of substituting y+1/y is to take advantage of the symmetry of the octic; you write {octic} = x^4 * quartic(x+1/x) for some suitablychosen quartic, and the 10^50+1 and 10^25 are from (x + 1/x) written as (x^2+1)/x.
