how to explain IOStat for 11.2.0.2 AWR

I noticed the AWR for a 11.2.0.2 database shows the following IO Stats I don't understand:

IOStat by Function summary
Function Name Reads: Data Reqs per sec Data per sec Writes: Data Reqs per sec Data per sec Waits: Count Avg Tm(ms) LGWR 0M 0.01 0M 1.2G 25.67 .331171 91.6K 2.19 IOStat by Function/Filetype summary
Function/File Name Reads: Data Reqs per sec Data per sec Writes: Data Reqs per sec Data per sec Waits: Count Avg Tm(ms) LGWR 0M 0.01 0M 1.2G 25.67 .331171 23 2.61 LGWR (Log File) 0M 0.00 0M 1.2G 25.66 .331171 8 3.75 LGWR (Control File) 0M 0.00 0M 0M 0.01 0M 15 2.00

The 'Waits' varies from 91.6K to 23 in two sections? Why the data are different? How to explain 'LGWR (Log File) ' only has 8 'waits' in IOStat by Function/Filetype summary'?

Thanks,
Lei

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