Usually, Uthra+ has 5 options:
Press "1": use it on cock
Press "2": use it on vagina
Press "3": use it on butt
Press "4": use it on chest
Press "5": use it on muscle
When your Tone = 0, Uthra+ should show a disabled "Muscle" button at position "5".
But actually, it shows the disabled button at position "1", meaning that you cannot use Uthra+ on your cock in this case.
Press "1": use it on cock
Press "2": use it on vagina
Press "3": use it on butt
Press "4": use it on chest
Press "5": use it on muscle
When your Tone = 0, Uthra+ should show a disabled "Muscle" button at position "5".
But actually, it shows the disabled button at position "1", meaning that you cannot use Uthra+ on your cock in this case.