The analysis service does have a (default) lag of 5 seconds, AND piont compression could play a role.
It is difficult to see when looking at the snapshot data what's going on. Could you show the archived values for the individual tags and the summation value? At least those timestamps should match.
Looking at the analysis Total Stream Flow is the total of your instrument tags and has 15 sec. AF analysis is having time lag in executing your analysis. Could you please let us know the scan frequency of your input tags?
High frequency input tags add delay to overall AF analysis resulting time tag. One work around is fixing overall time lag but depends on other calculations and other is moving towards periodic for the ones which are is consuming lot of time. Analysis is triggered based on latest timestamp of any input tag and if you see any incorrect results like out of order then request you to enable automatic recalculation.
On the same line of thoughts as Roger.
Do the archive values match up? If they do, then the issue is likely a latency. If they don't, then the issue is likely compression.