Huehn discovered an error in Donald Knuth’s book “Computer Modern Typefaces,” specifically on page Arabic one, in the very first word of the first paragraph. He notes that this volume is part of the Computers & Typesetting series as Volume E, which is why the memo field on his check reads “E1.”
After confirming the error, Knuth sent Huehn a reward check for $2.88, which appears on the check in hexadecimal notation as “0x$1.20.” Huehn has censored the check image because Knuth no longer hands out real checks due to security concerns; instead, recipients now receive a fantasy certificate from the “Bank of San Serriffe,” a fictional bank Knuth adopted for his reward program.
This image shows the check described in the second paragraph, where Knuth sent Huehn a $2.88 reward after confirming the error in the first word of the Computer Modern Typefaces book.
A few years later Huehn submitted another proposed error that Knuth determined was incorrect. Despite this, Knuth wrote several paragraphs explaining why the submission was wrong but still awarded a check for $0.32 because he counted a “throwaway sentence” in Huehn’s bug report as a good suggestion, illustrating Knuth’s practice of rewarding thoughtful engagement even when the claimed error is not correct.
This image corresponds to the bug report referenced in the third paragraph, where Huehn's later submission was deemed incorrect but Knuth still rewarded him for a good suggestion within the report.