[Koha] Item Number field

Hi, we're mapping the marc data (from a UKMarc export from Alice/Oasis) for our Koha install and the Items.Itemnumber causes an error unless it is set to tab -1. That is unless it is ignored and not managed by Koha. We need the item number to be information associated with an item, or some other way of doing an item count. What are we doing wrong? Robert McKenna Librarian Griffith College Dublin South Circular Road Dublin 8 Ireland 353 1 4150490