Discretionary FIFO is a first-in, first-out costing methodology at the discretion of the user. That is, with date-stamped batch tracking turned on, FIFO costing and consumption is available and recommended by the system but can be overridden by a user with sufficient privileges to select a newer batch (and therefore a more recent cost).
Accentis Enterprise will not mandate strict FIFO but rather recommend the ordering based on your own requirements. For example, your picking tickets will generally print the suggested batch number to consume based on your own FIFO rules, such as the use-by date of a product rather than the date on which it was actually received.