A few tips on using the search box on the Study page:

• You can input a kanji (Japanese character), keyword or a Unicode decimal point. The latter is rarely used, but it can be useful if you want to enter a story for a character that is not included in RTK. For example 22000 returns a page for 嗰 "Unicode #22000" (these characters have no preset keyword).
• To get an exact match add a space character before you press enter. This will prevent the dropdown from auto-completing the search term. This is useful with custom keywords, as the dropdown does not include your edited keywords (it is a known limitation for which I don't have a satisfying solution for now) (edit: to be precise, an exact match will be found if there is one, otherwise the closest match will be returned)
• The index numbers, and auto-completion of keywords is based on the original Remembering the Kanji keywords. It defaults to 6th edition. 5th edition can be set in Account Settings > RTK Edition.