iostat and awr File IO Stats difference

I been looking at some (10.2.0.4) on AIX 64 bit Awr report File IO Stats and can see that the Av Rd(ms) for some of the files are consistently above 50 to 60 ms over a 15min interval but when I reported this storage guy he mention and sent me the Iostat to prove that the service time in the same timeline is average of 20ms for the disk involve . What can cause the difference between the AWR and iostat readings

thanks

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