Also like Jason Perry posted, an average only tells a bit of the picture. They should at least provide a standard deviation. It should say something along the lines.
80% of cases 140 days +/- 10 days
90% of cases 140 days +/- 25 days
95% of cases 140 days +/- 40 days
If they did that then your level of certainty will increase. Also if you click the hyperlink of the phase. You will see a historical graph of the actual average for your UIC. It looks like the data is incomplete and they didn't do a good job of filtering out the 0 data, but once again it will give you an idea of your locations performance against the Army average.
So a quick way to estimate when you will be done with PEB is to take the last Army Delta Value and then add all the averages together. The last two values are for post transition and transition. So if you want to have a "rough" idea on when you will hit transpoc, take out those values. That is with an FPEB, take off those days if you want to figure without an appeal.
I will be curious to see how the averages change over the next month. I am going to keep a log in a spreadsheet and build a forecasting tool.