(Auszug aus "XSL-FO ― Die Referenz" von Manuel Montero Pineda & Steffen Herkert, 2016, dpunkt.verlag)
Category Extension for European Rule
Specifies the amount of space after the punctuation.
Formatter has extensions to customize the spacing around punctuation. These are used mostly for documents in European languages.
This block has the property language="en". This will cause the spacing extension to be applied and there will be 2 inches of space after the periods. The first block does not have language property so the extension isn't applied.