(ii)the amount of the development allowance, to the extent to which it has not been allowed as aforesaid, shall be carried forward to the following assessment year, and the development allowance to be allowed for the following assessment year shall be such amount as is sufficient to reduce the total income of the assessee assessable for that assessment year, computed in the manner aforesaid, to nil, and the balance of the development allowance, if any, still outstanding shall be carried forward to the following assessment year and so on, so, however, that no portion of the development allowance shall be carried forward for more than eight assessment years immediately succeeding the assessment year in which the deduction was first allowable.