Hi Lakshmipriya,
This is a product feature that impacts auto-close. Age old issue. That was one of the reasons I had put in an idea to associate workshift with autoclose - See here: https://communities.ca.com/ideas/235737304-ca-sdm-auto-close-association-with-workshift
Since I see you do not have many workshifts defined, you may try a trick but it will not work if you have general users associated to workshifts. It works perfectly, if the users do not need to have workshifts defined with their contact record.
Here is the trick:
(1) Rename the "Regular" workshift to say "Auto-Close".
(2) Change the renamed "Auto-Close" workshift configuration from the current definition to the one exactly like the "24 Hours" workshift.
(3) Create a new workshift called "Regular Business Hours" and define the business hours in your case. You can use this workshift for notification purposes or event triggering when a business hours schedule has to be followed.
If the 'Requester' does not have any workshift defined, the 'Auto-Close' will follow the modified workshift in (2) above and you should have the closure in 48 hours.
If this works, please vote for my idea above.
Thanks,
Indrajit Banerjee.