The variables .ls and .ss in utag_data object are used for managing session and visitor (lifetime) cookies in Tealium iQ Tag Management.
.ss - It stands for Session Start timestamp and is used for tracking the start of a user session.
.ls - It stands for Last Session timestamp and is used for tracking when the last user session occurred.
Both of these timestamps are Unix timestamps, meaning they represent the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, minus leap seconds.
Please note that these timestamps are integral to sessionization and visitor tracking logic, they can provide insights on user behavior on your site across different sessions.
Also note, different Tealium iQ Tag Management versions might have slightly different naming conventions or methods of storing these values. It is always recommended to refer to Tealium's official documentation or consult with your implementation team or Tealium representative for specific details.