You need to study math.
( If I want to make Lemon Chicken for supper, but the recipe I always use, to great effect, calls for half a can of frozen lemonade concentrate... but I don't have any frozen lemonade... I could convert the recipe from frozen lemonade concentrate to real, fresh lemonade, but calculate the water out, so as to concentrate it... therefore, if one full can is 355 ml, and if one whole can makes 4 times 355 ml- considering one usually has to add 4 cans of water... or would that actually equal 5 times 355 ml, because you've got 4 cans of water, plus one can of lemonade concentrate?.... and it takes 125 ml of lemon juice and 125 ml of sugar plus 800 ml of water to make one litre of lemonade... then how much lemon juice and how much sugar, would be in half a can of frozen lemonade concentrate...... so I should use the full amount of lemon juice and sugar that would be in half a can, plus half of 355 ml of water.... add to that the rest of the usual recipe ingredients... )
And you thought I had a cushy job.