You'll need to figure out an intuitive way to make use of the entry key: https://formidableforms.com/knowledgebase/graphs/#kb-entry or get the field ID of the user ID field for the form and use that in this case: https://formidableforms.com/knowledgebase/graphs/#kb-field-is-equal-to

However, I believe formidable gets the formidable user ID (numeric) by default and displays user meta instead (via php on the numeric ID). If you want to use user meta, you'll have to work with this: https://formidableforms.com/knowledgebase/user-registration/#kb-autopopulate-forms

So them maybe something like:
[frm-graph fields="64" user_id="current"] or [frm-graph fields="x" y="[user_meta key=user_email]"] (x is the user ID field and y is a field ID that holds maybe the user email).