Event Summary Value error "null_not found field" - Agentblazer

I'm on the steps for event summary (copied steps below).

• In step 2 it says to copy the value and paste it
• I've gotten an error message from this copied value

  Has anyone else had this error and been able to fix it? See attached image of error message.     

1. Click the Event Summary element.
2. For Value, copy and paste this:  Check-in date of {!Reservation_1.Check_in_Date_c__c}, check-out date of {!Reservation_1.Check_out_Date_c__c}, for room type {!Reservation_1.Room_type_c__c}.
3. Click outside the Value box so the Save button becomes available, then click Save.
4. Click Activate.
5. Close the Flow tab.