Ignore individual spikes unless your getting alot of those. peaks are what matters most in PIF testing. PIE are correctable errors so even above 280 you will not have playback issues unless your PIFs are considerably above 4 (scanned at 1ecc, 12 if using cdspeed and benq drives at 8ecc).
The issue with high PIEs though are that some players (home dvd players as well as computer dvd roms) cannot handle high amounts in one ecc block (what a peak represents) I.E. more than 4 PIF errors (uncorrectable) in 1 ecc block which can cause issues with playback, skips and freezes.
With that said having high PIEs alone can become a issue later on even though playback is ok for now. They have a tendency to raise over time (due to dust, time, etc. ) so your playback may be ok for now (pifs are still tollerable) but later with time you develop higher PIEs and thus causing more higher PIFs which then result in a skipping or pausing disk.
So Lower is better rule of thumb..this of course doesnt address Beta and Jitter which can cause playback problems as well. From what ive seen though Beta and Jitter are usually only high when you have PIF issues.