The viewer remembers the extension times that were set for an item when you use ‘use fits’ in the slope editor. The extension times are stored alongside the settings for the slope onset and offset. After you have used ‘use fits’ for an item the item’s saved extension times will always be used when viewing that item, the item’s extension time value won’t change until you set a new extension value and save it again with ‘use fits’ again.

The default extension time which is set by selecting options=>set extension times   in the pull time menu will be used whenever an item has not had its extension time set by selecting ‘use fits’

The workflow would be something like this.

When an item is first viewed in the main window, it does not have a saved setting for the extension time, so it uses the default value.

You can change the value in the bottom left hand ‘current segment time extension’ setting box, this won’t be remembered at this point, so if you go to the next item it would be discarded. If however you change the current segment time extension value and go into the slope editor, the slope editor will be using that current extension value

If you then select ‘use fits’ the value shown for the current segment extension time will be stored for the item, this stored value will be used for subsequent operations for that item.