In case an injury causes more than one permanent disability specified in ss. 102.44 (3), 102.52 and 102.55, the period for which indemnity shall be payable for each additional equal or lesser disability shall be increased as follows:

   (1)   In the case of impairment of both eyes, by 200 percent.

   (2)   In the case of disabilities on the same hand covered by s. 102.52 (9), by 100 percent for the first equal or lesser disability and by 150 percent for the 2nd and 3rd equal or lesser disabilities.

   (3)   In the case of disabilities on the same foot covered by s. 102.52 (14), by 20 percent.

   (4)   In all other cases, by 20 percent.

   (5)   The aggregate result as computed by applying sub. (1), and the aggregate result for members on the same hand or foot as computed by applying subs. (2) and (3), shall each be taken as a unit for applying sub. (4) as between such units, and as between such units and each other disability.