The user had two questions on the HR list-view "SLA" column:
To answer the first question:
The SLA column of the HR Case table is updated via Business Rule (henceforth "BR") "Populate case SLAs", which lives on the task_sla table.
Whenever a Task SLA record is inserted, or an existing record is updated or deleted from the form, this BR updates the SLA value in the corresponding case record.
Now this Task SLA record is updated due to one of the following reasons:
Whenever a user opens the HR case, the SLA value gets recalculated and is updated in the record (if a certain SLA system property, "glide.sla.calculate_on_display" is set to a value of "true"). So this is the reason that while looking at the HR case list-view, a user will see the older SLA value but when they open the form-view, it starts displaying the recalculated value (this, again, is due to the SLA-related system property referenced earlier).
To answer the second question:
When multiple task SLAs are on a case, the HR case record will simply store the SLA value from the most recently updated task SLA record, whichever task SLA record that may be.