Try the search below:
index="view" Activity="viewdocument"
| rangemap field=Duration "0-3sec"=0-3000, "3-6sec"=3001-6000, "6-10sec"=6001-10000, "10-15sec"=10001-15000, "15-20sec"=15001-20000, "20-25sec"=20001-25000, default=">25sec"
| stats count as Count count(eval(range="0-3sec")) as 0to3sec count(eval(range="3-6sec")) as 3to6sec count(eval(range="6-10sec")) as 6to10sec count(eval(range="10-15sec")) as 10to15sec count(eval(range="15-20sec")) as 15to20sec count(eval(range="20-25sec")) as 20to25sec count(eval(range=">25sec")) as grt25sec
| eval Percent0=0to3sec *100/Count
| eval Percent3=3to6sec*100/Count
| eval Percent6=6to10sec*100/Count
| eval Percent10=10to15sec*100/Count
| eval Percent20=20to25sec*100/Count
| eval Percent25plus=grt25sec*100/Count
... View more