Hidden "Visibility" field, under Attachment

Hello experts,

We're trying to hide a field named "visibility" which stays under "attachment" button, on master agreement.

Our problem here, is that we already checked out the "reference guide", get all the information we needed but the sourcing doesn't hide it.

I'll put some print screens so you can understand is better:

1) Created a new Master Agreement

2) Clicked on "attachments" button

3) After attaching a file, the field "visibility" appears.

4) Clicked on "Reference Guide" to find the field name and description

5) Under "Page Customization", put the value over the property, but it didn't work and the field is still appearing.

Can you guys help us out ?

Thank you !

R. Navajas