851.9. Where, at a particular time, the fair market value of property from a segregated fund transferred by an insurer results in both a decrease, at that time, in that portion of the insurer’s reserves in respect of a segregated fund policy that vary with the fair market value of the property of the fund and an increase in the portion of those reserves that do not so vary, the amount of that increase is deemed, for the purposes of computing the income of the insurer, to be a premium received by it at that time.