formulation problem

[hjq0523]

I cannot understand the formulation：
outs[row_ind:row_ind+length, 0:2] = (outs[row_ind:row_ind+length, 0:2] * 2. - 0.5 + np.tile(self.grid[i],(self.na, 1))) * int(self.stride[i])
outs[row_ind:row_ind+length, 2:4] = (outs[row_ind:row_ind+length, 2:4] * 2) ** 2 * np.repeat(self.anchor_grid[i],h*w, axis=0)
would you please help explain it