The serial number on the example of this type of this error in Charlton's is EVY2180764...could the original poster's note have come from the same sheet?? I am by no means a wizard on plate / position numbers like others on this forum!
I would think that the two notes (the one shown above and the one pictured in Charlton) came from the same sheet. They are the same prefix and have nearly the same last 3 digits (264 and 764). This type of error just does not happen again and again.
Unfortunately, I am not an expert on the Birds series notes. Numerous papers by Don Roebuck were published about the series, and I'm sure they would be of some help in figuring out position number and serial number layouts, though I would advise caution as printing practices were changing toward the end of the series. We know the start of the series used some predictable patterns, and sheets of 40 notes were sold to the public with a skip interval of 500. But the Birds $20 note was the last denomination to be succeeded by the Journey series, and we know the printing company (CBN) went to a 45/on skip-8000 format. Outdated information carried into the Journey series... insert note ranges of 45,000 notes were shown to be irreconcilable with the numbering practices that were uncovered. So when I look at insert note ranges of the late Bird series and see ranges of 18,000 and 36,000 notes (or multiples thereof), and then I look at these two error notes that are 280,000 numbers apart but apparently from the same sheet... and I say "Hmmmmmmmmm... something does not fit here." It is very possible that CBN was using a split layout in the sense that notes across a row were skip-numbered by 500, but skip intervals down the columns were much larger. It could be another case of mini reams and mega-sequences! Even researchers get very quiet when they hear those words tossed about!
So anyhow, I think that this error type is priced conservatively in Charlton. I think a dealer would know this and would pay the $2750 for this note without much hesitation!