Tag History calculate fill rate

I have a tag that we are currently storing history on, it is a fill % tag. I am looking at rough guessing a fill rate by taking the last 6 hours of data of that tag, take the range and and divide that by 6 to get a % per hour, and multiply that by the remaining % in the tank.
When I do a tag query for history, and I select Range i get 360 rows, I was expecting to get 1 row based off the description.

Is there something I am missing on the best way to get this range? I would prefer to have this live as a tag instead of on a page only.

Hi stuartd,
The Range Aggeration Mode will return the range between the highest and lowest value for a given time slice. The number of values within a time slice is determined by the Sample Size properties.
Because the Sample Size you selected is Natural , it will look up the logging rate for the queried tags and return results spaced apart at that rate.
If you want to return the range value of the tag in 6 hours, you might change the sample size to Interval and set it to 6 hour.