Only first 8 returned values from discovery are being processed and itemized, rest is discarded. Below you'll find an example I came across just yesterday:

net.if.discovery returns 12 unique interfaces: lo, eth0 through eth7 and bond0 through bond2 (in that order). Discovery rule fiter has regex: ^[^l][^o] to omit the loopback interface. After this is done only items for eth0 through eth7 are created.