02519/20 was scheduled to start from October. After the press release for 02520, one more release came having the same train number scheduled for two runs in September. Subsequently, the same was updated at IRI for 02519/20.
Later one more release came that the train having run in September (Originally numbered as 02519/20) was renumbered as 22519/20.
While 02519 run was corrected, but 02520 wasn't. Hence the confusion.