You have a couple of options.
I’m assuming your
TaskIssuedDate field is a formula field with a formula of
CREATED_TIME(). If so, then your
ElapsedDays field would also be a formula field, this time with a formula of
TONOW(TaskIssuedDate). This will display the current number of days since the record was created.
If you don’t need to store
TaskIssuedDate explicitly, and you can safely assume the date the record was created is also the date the task was assigned, you can simplify things a bit by changing the formula for
TONOW() returns a
string consiting of a numeric representation of the days elapsed concatenated with " days" – for instance, “12 days”. string representing a ‘friendly’ presentation of the amount of time pending or elapsed: e.g., “12 days”, “1 month”.