Delta action="add"

1)Delta action="add" means what ??

I Dumping file 'C:Program FilesSAP Mobile InfrastructurelogsmartSyncInboundTmp.txt'

I End of content of file 'C:Program FilesSAP Mobile InfrastructurelogsmartSyncInboundTmp.txt'

2)Conflict: R/3 = delete, device = modify

why device modify will trigger a delete in R/3 instead of modify