"The highest ranked candidates are invited during rounds of invitations. If we issue 3,500 invitations during a round, the system will pick the top 3,500 candidates at that time."This one,
http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=1318&top=29
See the last two lines of the table, the ones with status still in pool
I think 423 is written by mistake, but it is very hard to swallow that CIC could make that type of mistake.