Answer:
If the nearest hazard zone is at least 1.1 m away from the ground slot, the distance that the protective fence to the ground (or to the plane of reference) has to have may be up to 18 cm.
 
If the nearest hazard zone is at least 85 cm away, the distance to the ground may only have a maximum of 8 cm.
 
Distances greater than 18 cm are prohibited, as they allow a full body access according to the standard.
 
If the distance to the nearest hazard zone is less than 85 cm, the ground slot may only be 2 cm or less.
 
Or put another way:
An arm will fit through a slit over 2 cm. This results in a safety distance of 85 cm to the nearest zone of danger.
A leg will fit through a slot of more than 8 cm. This results in a safety distance of 1.1 m.
An entire body fits through a slot over 18 cm. They are prohibited.
 
If you have other measurements in mind on this subject, such as
34 cm or 66.5 cm to the hazard zone, with 20 cm ground clearance, read on here.
 
If you want to use an answer for your risk assessment, please buy the Standards research, check it, and also check very carefully if the given case really applies to your machine. If you have any doubts, feel free to contact me.
Please remember that there could be C- Standard specifically for your machine that contains statements on the subject. My statements refer to the B-Standards. If you provide me with your C-Standard, I will research your C-Standard on the subject.