When you bring a new recipe file into Mangia!, it carries a little dictionary along with it for the terms it uses. The first time you open the file, we need to do a little work to reconcile any inconsistencies between its dictionary and Mangia!'s own dictionary. It doesn't take long, but you may be asked to make some judgements about how close entries in the two dictionaries really are.
If you're opening an enormous recipe file on a tight hard disk, you should realize that this process creates a file that is as large as the file you're opening. Although it gets deleted at the end, you do need enough spare space at the beginning.