Performance measurement with v$asm_disk_stat

Hi,

I built a Excel spreadsheet to analyze 2 snapshots of v$asm_disk_stat. As I'm seing strange results on some disk groups, I would like to confirm with some experts here, that my formulas are rigth...

I query v$asm_disk_stat at an interval of 4 hours and I compute the différence between the 2 snapshots :

Here  is an exemple of number:   

PATH	Diff Reads	Diff Writes	Diff Read Time	Diff Write Time	Diff Bytes Read	Diff Bytes Written	Rate Read (MB/s)	Rate per Read (KB/read)	Rate Write (MB/s)	Rate per Write (KB/write)
/dev/rhdisk17