It's poorly worded, but from Wikipedia there is a more general formula that the amendment hints at but doesn't state.
Historians (myself included) and political scientists, following the lead of Clinton Rossiter’s 1966 study of the American founding, have misunderstood and overlooked Madison’s unratified first amendment, some assuming incorrectly that it would have fixed congressional districts at 50,000 inhabitants. Such a mandate would have required an unwieldy body of 5,200 representatives by the last decade of the twentieth century. In reality, Madison’s formula was far more modest. After the 1990 U.S. census, district size would have been set at 170,000 rather than 572,467 residents, and the House of Representatives would have had 1,465 members. Twenty years later, in response to the 2010 census, the formula would have raised the size of districts to 190,000, instead of the average size of 710,767, and the House would have had 1,625 members, in place of the current 435-seat limit.
— Kyvig, David E.., " Explicit and Authentic Acts ", Chapter 19, University Press of Kansas. ISBN 978-0-7006-2229-0” (2016)
For 2010 census, there would be around 1625 districts of 190,000.
Hey, it'd still be smaller than the Chinese National People's Congress.
