SAP Message 37218 - Use at least the defined length &

Diagnosis
You are editing an input/output field on the screen and have entered adefined length of less than the minimum possible length.
If the input/output field has no icon, you have entered 0 as thedefined length. This would correspond to an empty field.
If the input/output field has an icon, you have specified a length thatis insufficient for the system to display the icon. Input/Output fieldswith icons use the first four characters to identify the icon, and thefifth to separate the icon from the subsequent output template.

System Response
The system cannot accept this value for the defined length.