First of all, there is no season 8. Why would it jump from 5 to 8? Also, there are 4 unknown season episodes. They should all be deleted. Three of them already have pages and the other one is for the opening credits. This is not an episode. Seriously, who confirms these edits?
Looking at the series for Hey Arnold! here, I noted that currently there are only 5 seasons listed and 4 "unknown" episodes. The incorrect season 8 appears to have been removed, so the only remaining issue is the 'unknown' episode entries.
David - as bluesmanSF mentioned, if these are duplicate listings please merge them to the correct episode:
To submit a correction, you should use the 'Title Correction' option to change the title of one episode to the second. For example, if you know that the pages for Untitled XYZ Project (2006) and ABC Movie, The (2006) refer to the same film, you would go to the page for Untitled XYZ Project (2006), click on the Edit Info button at the bottom of the page, select the 'Title Correction' option and change the title of the film to ABC Movie, The (2006). This will result in a merge of the two titles.