Hi Rachel,
That helper text is built into the multi-select field type to make sure it is giving clear directions to users on the limits for the field so there is not a way at this time to disable it from displaying on the form. If being able to hide this is something you need to make better use of Quickbase I would recommend adding it as feedback on our User Voice.The Quick Base User voice can most easily be accessed from the My Apps page in Quick Base by clicking on the orange Feedback tab that appears on the right of the page or at
http://quickbase.uservoice.com by signing in with your Quick Base credentials. If you have any trouble signing in directly with the URL going through the Feedback tab on the My Apps page most often resolves them. (I will give the note that we will be moving from User Voice to a new platform in October so these steps will be changing in the near future but any ideas put in today will be transferred over to our new feedback platform)
------------------------------
Evan Martinez
------------------------------