If we use a NotforLoan value of a positive number, the item does not allow holds and shows in opac-search.pl with the status "Available for Reference." If we use a NotForLoan value of a negative number, the item does allow holds and shows in opac-search.pl with the status "On Order." There's an assumption here that items that don't allow holds will always be reference, which isn't always the case. Some libraries wish to show On Order materials in the OPAC, label them as On Order in opac-search.pl, and block holds.
This bug is being looked into and repaired to fix the problem of On-Order records being available for loan or reference in this case. This needs to cleared up quickly because it affects all item types that are Not For Loan; which includes discard. The item that shows available for reference is in the recycling bin.
Hi believe this is resolved with the Reference_NFL_Statuses system preference. It allows to configure which status show as reference/for loan and it works with -1 (just tested)