Choose a visible length between & and &

What causes this issue?

You want to change the visualized length of a screen element of type
input/output field.
Reducing the visualized length results in a narrower field area in
which rolling is possible at runtime in the maximum length of the
input/output field.
If the screen element does not have the attribute "with icon", the
maximum runtime length is identical to the defined length.
The value you defined, however, is larger than the maximum length of
the input/output field at runtime. Rolling is therefore not possible.
If the output field has the attribute "with icon", the defined length
must be large enough to be able to hold the internal representation of
a field with icon and possibly with a separate quick info at runtime.
The visualized length can (and usually is) much smaller because at
runtime the screen does not have spearate space for the quick info.
The value you defined for the visualized length, however, is so large
compared to the defined length that it cannot be fully used at runtime.

System Response

The system does not use the value for the visualized length.

How to fix this error?

Use a value from the value range suggested in the error message.

Error message extract from SAP system. Copyright SAP SE.