This has been a long time since I have done this, but have you looked into First Articles? Instead of looking into inventory setups (LOT size and multiples)….look at setting up first articles.
You basically add more material to create “extra” pieces” that you either use up to destroy or can move on to real production.
Also, an operation on a method has a field for scrap by quantity or percent. I think this is what you may be thinking. So if you have a lot multiple of 25, no max lot (or large such as 200) and a scrap percentage of 4%, you should have what you’re looking for. For example, a quantity of 67 would produce a job with an initial production quantity of 78, driving materials for 78: 75 for completion and 3 for scrap on the operation in question.