Question for the mothod "coset_fft"

[simplelins]

`fn coset_fft_in_place(&self, coeffs: &mut Vec<BlsScalar>) { Self::distribute_powers(coeffs, GENERATOR); self.fft_in_place(coeffs); } pub const GENERATOR: Scalar = Scalar([7, 0, 0, 0]);

`

for the 'GENERATOR', why we use this value in Montgomery form, but not a int value '7' convert to scale. I checked the libsnark that need convert a bigint(int:7) to a scale and then to use at coset_fft.