In classic list views/forms and on-premise environments, your choice columns allow you let users specify their own value. But the label is literally “Specify your own value:”. This can be changed.
Note: If you’re using the modern experience, you don’t have this issue.
To change the label, add the following script to your newform.aspx page, changing the name of the field referenced (see below). You can add this script in a script editor web part as a snippet or save it as a .js file to your Site Assets and reference it in a content editor web part.
To get the actual field label, use F12 (developer tools) when viewing the form and select the checkbox. Copy everything after the ‘#’ sign or whatever the column name is, ending in ‘FillInRadio.’
Once you’ve added that script (and updated the field name with your own), save the page and you’ll see your new label: