At a local garden centre restaurant...when one sign might not be enough, use an exact duplicate alongside to re-enforce the point.
But lots of other revealing interest here too....
Firstly it's a message targeted at staff but it's a big message on prominent public display, and of course duplicated too. The design effort in creating an atmosphere and ambience for diners, can be somewhat diminished by this.
Secondly, there a curious tautology going on here. It's a staff notice, telling staff that it's not for staff use. So is it must be for public use. But the notice's target audience is staff - given the clear 'Staff Notice ' header. So if you're a member of the public, despite the prominent public and duplicate display it's not for you.
Thirdly, the definition of "use" in this case can be seen three quite distinct ways ways. Either it's use of the first aid items by the staff for their own injuries. Or it's the use of the use of those items by the staff for customer injuries. Or it's the use by customers for their own injuries. In practice it's the middle one of course - that's the whole point of having a first aiders. The sign's really about discouraging the use by staff for their own injuries. There'll be a separate staff first aid box with different things in - for example different colour plasters for use by staff to ensure their injury is prominently treated.
The reality here is that the sign's a substitute for something missing around staff policy, training or awareness. There's a fair chance that perhaps one member of staff once used something from this first aid kit for their own care. But the corporate reaction rather than being targeted and specific id generic - duplicate signs targeted at all staff on display to all customers.