The difference between enqueue waits in V$SYSSTAT and enqueue waits in V$SYSTEM_EVENT is that the later counts distinct (normally 3 second) waits whereas the former counts logical waits but only once they have been resolved. Therefore, you may have had more than 23 logical waits, if some sessions were still waiting.

I have an OLTP with an intermittent performance problem. Having run utlestat, I have the following concerning stats:

From the "system wide wait events - non background" section:
enqueue total:1,157,903 ave:59.39 cnt:19,498

From the "Statistics" section:
enqueue waits total:23

I've looked at note 62161.1 on MetaLink and this seems to suggest I had 23 locks in the period that waited on average 8 minutes.