Requested by is displayed instead of Number under catalog task

1) Navigate to sys_dictionary

2) Filter the list:

Table: sc_request

Column Name: requested_for 

3) Open the Dictionary Attribute Record.

4) Open Dictionary Override for Opened By on sc_task table:
You will see "Override display value" is set to "True" and "Display Name" is "opened_by", which is the reason why "Opened By" is seen in place of Task Number.