Unlike titles going to PER or most other locations, titles going to MAIN (a lot of which are standing orders and continuations) should not have the call number label placed in the upper left-hand corner. Rather, the call number label goes either on the bottom of the spine, if the spine is wide enough for the call number label to fit, or if the spine is not wide enough, the call number label should be placed in the bottom right corner of the outside back cover. Feel free to trim blank parts of labels.
The two options for call number labels on MAIN items:
Check out the labeling page for general instructions regarding labels.