According to the Data Dictionary, the Display field can be 120 characters, while the displayascii field is only 30 characters.
2.3.98.5 display (FI-317)
Type: string [120]
Default Value: EMPTY
Validation: ^[^]""""%<>[&|{}]{0,30}$
Migration Source: NumPlan.Display
Remarks: The localized name to display for internal Caller ID
2.3.98.6 displayascii (FI-1789)
Type: string [30]
Default Value: EMPTY
Validation: ^[a-zA-Z0-9 !#$'()*+,./:;=?@\\^_`}~-]{0,30}$
Remarks: A safe version of the Caller ID Display text using only English letters (a to Z) and punctuation, used when endpoints are using different language groups.