garbage collection - Understanding Java's GC logs -

I turned on Verbose GC option on my JDK, and now I have lines like

 [CMS -Compatible-sweep-start] 25.622: [CMS-concurrently-sweep: 0.023 / 0.024 seconds] [Times: user = 0.02 sys = 0.00, actual = 0.03 sec] 25.623: [CMS-concurrently - reset-start] 25.629: [ CMS-concurrent reset: 0.007 / 0.007 seconds] [times: user = 0.01 sys = 0.00, actual = 0.00 seconds]  

Anybody can tell me exactly Is

1. CS + users and what is the difference between the real-time?
2. What does "0.023 / 0.024 seconds" mean? According to

   , two numbers 0.023 / 0.024 are CPU / wall bars