"Cannot create a valid field value for the column heading 'Difference in days between [Current DateTime] and [.pySLADeadline]'. The text will not be localized. Field Value Difference in days between [Current DateTime] and [.pySLADeadline] : length exceeds 64 characters."

I am getting the above warning when I add a lengthy column name, I need the lengthy column name also to be represented in the report definition column. How can I solve this? I used field value and called the field value ID in the column field in report definition but when I click Action->run field value is not working. Is there a proper way to call field value?