4. A leave account shall be kept for each Judge showing therein the amount of leave due to him in terms of leave on half salary and in such account there shall be- (1) credited to him in two separate columns- (a) a period equal to one-fourth of actual service; and (b) where any duties not connected with the business of the Supreme Court are assigned to a Judge and, for reasons of such assignment, the Judge does not avail of any vacation or avails of less than thirty days of vacation in any calendar year, in addition to the leave credited under the preceding sub-clause, a further period equal to double the period by which the vacation availed of by him falls short of thirty days; and (2) debited to him the period of leave on full or half salary granted to him: Provided that the opening credit at the commencement of this Ordinance shall not exceed six months in the case of any Judge.