The Tickets table view is providing the possibility for agents to setup their own column view of the tickets. This settings is unique for each agent and they can create it for themselves.
The Table view will always start with the Contact then the Subject of the ticket. This is fixed in the view.
In the Contact column it will show the profile picture also for the Contact. And at the end of the Subject line the Ticket# will be visible.
Everything coming after this two is customizable for your own preferences. Show only what you want to see in the order you like to see it. These are fixed width so if you add too many they will widen the view for you and you will not see everything.
The group and the agent is a combination so you see both of it if you turn this on however placing this to the last position on the list will allow the name of the agent to not be visible fully as well limit the width it would take up.
You can select all the properties of the Tickets you see as well as fields like Created At or Waiting since

The Waiting since refers to the time gone since the customer replied and waiting for a response email to be sent. 

The Created At is the time stamp when the ticket is created from the email.
To modify the various columns you see - and this setup is only going to be visible for you - you need to click on the pen icon on the right hand side end to open up the settings window for it.
Once you click the pen, it will open up the scrollable list of the different properties you can select and arrange in order.
On the top is the Fixed Columns which is the Contact and the Subject. These cannot be moved or removed.
The next part of it is the Columns you've added to the display. With the Red (-) icon you can remove them from the view and with the three lines you can drag them to reorder it.
Under the fixed and added columns are the ones listed are the columns that can be added to the view. Clicking on the green plus symbol will add them to the list as the last column.
If you wish to, you can add all the columns to the view. If there are too many added you will be able to scroll left and right on the view.