How can I make a summary field display the numeric result in the format of hours and minutes?
Sounds like you're starting with time periods in decimal format, aggregating them in a summary field and then wanting that to display in hh:mm format. Correct?
The summary field is just going to be a number type. Then you need a calculation field using GetAsTime(summaryField). If the source data is not in seconds, you'll have to multiply it by 60 or 3600 inside the function depending on whether it's in minutes or hours.
Here is a custom function I created that references a nominated field:
Int ( timeField / 60 ) & "hrs " & Mod ( timeField ; 60 ) & "mins"
I use this to display total time on a job, referencing a Sum field in a line item table where task time is recorded as a simple number of minutes. You could easily deploy this as a simple Let() calculation.
Retrieving data ...