The value in the parenthesis is the implicit parameter and the item itself would be the specific parameter, procedures that do not have specific parameters, use implicit parameters, the fillTank strategy has the two an express and an implicit parameter. Allows just take a closer consider the fillTank approach in https://spencervuqmh.thenerdsblog.com/34401826/the-smart-trick-of-free-this-jav-that-no-one-is-discussing