Hello @Ruchika_Abbi1 
I've found that same things on that New Project Management Template.
See the field type icon is same as Autonumber. But there are no specific setting to set it as like it set on that Manual Sort field.

If someone has idea then give more info.

@ScottWorld @kuovonne @Sho @TheTimeSavingCo 

@dilipborad 
Just found details of it in this thread
https://community.airtable.com/t5/interface-designer/when-working-with-interfaces-is-it-possible-to-manually-sort-a/td-p/168322

Hello @Ruchika_Abbi1 
You have an incredible eye for detail!
You're right it's related to interface only. When I create new manual sort field on that interface side I found that new field is automatically create on Data side.

👍