Google Drive Search: Filter Files by Modified Time in Lindy

I'm trying to setup a lindy that searches a google drive for files created within the last 4 hours, then sends an email summary if anything is found to a email address. I'm not sure what syntax I can use for the search field. I know I can use: modifiedTime >= [startedAt] Where modifiedTime is from the Google API docs for Drive, and [startedAt] is inserted by lindy - but how can I do math here to subtract 240 minutes from startedAt?