B’shas Hadchak means if you want to put milk in your coffee and there is only Clolov Stam on the table, so you can use C.S.; or if you want a Hershey Bar and there are only C.S. Hershey Bars, so B’shas Hadchak you can eat the C.S. Hershey Bar. Or if you are shopping at the A&P and they only have C.S. products and not C.Y. so B’shas Hadchak you can buy the C.S.
But, if when you want milk in your coffee and there are both C.S. and C.Y. milk on the table, you should use the C.Y.