When bulking by vendor, the item totals are calculated based on how many of each item not available is requested. The one thing to note is OPS decides whether to order from the library (in-stock) or Bulk order console based on IF the quantity requested IS GREATER THAN the quantity available. So, if you have 10 available items in the library and you order 9 it will order all from the library, if you order 11 it will order all items from the vendor. OPS does split up library requests, some line items get ordered from the vendor, and some get requested from the library based on availability. However, it cannot split up line items into separate orders (ie. 10 of the same item from the library and 1 items from the vendor). That is a little like splitting hairs.
This is a non-issue for teachers because they rarely need to order more than one of the same item for a student. For admin/library staff ordering large quantities of items from the Library Database, PLEASE REVIEW the number available before ordering. If there are 10 and you need 11, then you first need to make a request for the 10 (to be requested from the library), then make a second request for 1 more which will be ordered from the vendor in the bulk process.