The number of target instances that can be linked to each source instance. 0.1 = the link is optional; 1 = there must always ...

The number of target instances that can be linked to each source instance. 0..1 = the link is optional; 1 = there must always be one target for each source; n..m = there must be at least n and at most m. The upper value m can be *, meaning no limit.