Whenever a person's filmography is displayed, the order of the categories is based on the number of credits in each category. For example if someone has:
their listing will display in the order:
Episodes are counted individually
Because episode credits are also factored in, it may appear like a smaller category is listed first. Double check that the person is listed on the exact episodes of a television show that they worked on, in order to ensure the correct ordering.
"Self" credits and "Thanks" credits always appear as the last categories on the page, regardless of the number of entries.
This order isn't meant to imply anything about the relative importance of the various credits. It's just a technical convention. This is a software-dictated function which applies to all filmographies in IMDb and cannot be changed.