The Rail Delivery Group made a change to the way discounted fares are calculated earlier this year. See https://www.bbc.co.uk/news/articles/cpw8j4d1v2do for more details. As a result of this some railcard single fares on Oyster now cost slightly more (5p, or possibly 10p) than they did at the last fares change in March.
The somewhat disturbing side effect of the recent cyber security incident is that the database that drives our fare finder, as well as TfL’s own single fare finder, has not yet been updated. TfL make a big thing of checking what your fare will be, so it’s disappointing to know that the official source is out of step with the live database.