Cross Reference cards in "United States Index to General Correspondence of the Pension Office, 1889-1904"

That is a limitation of the index.  There is no longer a room 522.

What do you think was the subject of her query?  You can try to look under subject headings.

Dear Ms. Boutilier,

Thank you for posting your question to the History Hub.

The National Archives Catalog entry for the “Index to Document Files and Record Cards, 1889-1904” that you were using on FamilySearch.org can be found here: https://catalog.archives.gov/id/588793. Both the index and the records it relates to are in the custody of the Textual Reference Branch at the National Archives in Washington, DC (Archives I). You may wish to contact them directly at archives1reference@nara.gov with questions about the series.

In general, it appears that the index card for Ida Eggeling in this series refers to a further index. As Mr. Deiss indicated, “Room 522” most likely does not exist now. The card was stamped while the records were in the custody of the Pension Office--and before the establishment of the National Archives. The card most likely refers to something like these “Indexes to Letters Received, 1880-1894” (https://catalog.archives.gov/id/607987), but we recommend that you contact the Textual Reference Branch at Archives I for more assistance locating the specific index.

Thank you, again, for sharing your question with us, and best of luck with your ongoing search.