Is it attached to a value list with the number 1 in the value list?
No the value list is test and tes
Select the field while in layout mode and check the Behavior settings found on the Inspector's data tab. Is it possible that the check box permitting access to the field in browse mode has been cleared?
If that's not it, look for a script trigger "badge" in the corner of the field. If there is one, right click and check for script triggers to see if there is a script that may be either preventing the field from being modified or changing the value after it has been so modified.
And you can open Manage | Database | Fields and check to see if an auto-enter calculation was specified for the field that might modify the data entered by the mouse click to become something that is not listed as a value in the value list specified for your check boxes. (You might even make a copy of the field and return the copy's format back to edit box so that you can return to Browse mode and see what data if any is actually in the field.)