From context, I got the strong impression that the gadgets came with the office and Dumbledore is speaking about the work of deciphering what each one is measuring. If he was creating that device, why would he speak of the 8 hands as one of 'them', the 'they' that 'came with the Headmaster's office', most of which he has not figured out - except this one which records X...
Um.... No, he didn't create them. It says right in the quote that they came with the office.
Question is.... How did he figure that one out? 'Number of orgasms by left-handed witches in France'; that isn't the kind of data you'd find written down somewhere.
(The HPMOR discussion thread after this one is here.)
The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: