I’ve clicked ‘Calculate Cap Rules’, resulting in a new Y-OTC row. Where did the chartstring for this row come from?

Newly created Y-OTC rows by default use the chartstring from the position’s funding entry default funding profile. Despite this default, you are able to update the chartstring on the Y-OTC row to another unrestricted fund. 

If there is no default funding profile associated with the position, the chartstring fields will be blank, and require you to manually enter an unrestricted chartstring.