This is a good burn, but not a great burn. We're mostly worried about maximum values for both the PIE's (top graph) and the PIF's (bottom graph), rather than the totals, since a high peak presents an immediate danger to a successful burn.
Your max PIE is 55 (it happens near the beginning of the burn), but it mostly hovers around 40. This is an OK level, but a great burn would would have PIE's that peak below 20 and hover anound 10.
Your PIF's (generally considered to be the most important numbers) max out at 7. This is what gives you the CDSpeed "Quality Score" of 96%. So as far as CDSpeed is concerned, this is a very good burn.
Your PIE total is 353,037. I like to see this total below 100,000, and I've often seen it below 10,000 for a truly excellent burn. But I've seen totals higher than 2,000,000 and the DVD is still readable (but it's usually marginal at this point).
Your "PI Failures" total is 2535. I like to see this below 2000, but 2535 is not high enough to worry about. This shows that most of the PIE's were corrected by the first layer of error correction data. Note that the "PIF's" represent the small fraction of "PI Errors" that were NOT corrected by this first layer of error correction data - and hence the name "PI Failures".
Fortunately, there's a second layer of error correction data will easily correct the remainder, since the PIF maximum is only 7 (and for the BenQ 1620, any value below 16 is considered to be safe).
In short, the BenQ is burning these discs acceptably, and your burn is NOT a marginal one, but a good one. That said, the disc may still not read in all of your players for the following reasons:
Some players simply don't like playing certain discs, regardless of how well they scan. A good scan does NOT guarantee that the disc will be universally accepted, particularly in an older player. It merely tells you that the burner is properly burning the disc. If it fails to read in one of your players, then try a blank disc from another manufacturer. And sometimes it's simpler to just buy a newer player.
There continue to be persistent reports of issues with the BenQ 1620 and "-R" discs not working in some players. It's still my opinion that it's a bit safer to go with "+R" discs when it comes to the 1620, but I know others will disagree with this assessment.