R-class range and intelligence assumptions

Why did German intelligence underestimate the R-class battleships' operating range?

German analysts assumed British claims were inflated and did not credit improvements or additional usable fuel capacity, leaving them below the ships' real endurance.

German intelligence underestimated the R-class battleships because it did not believe the Royal Navy had improved and maintained their range. German estimates started below the published British figure. The ships then performed slightly better than that figure because they could carry more usable fuel than expected. Fleet endurance depended on maintenance and actual fuel capacity as much as the published specification.