OK, this is slightly OT being about train travel, but these are my connecting trips from/to international flights, so I hope they qualify.

Trying to book Shatabdi tickets at IR website, one option is to check the box to to "Consider for Auto Upgrade". If you know the system, are they talking about:

1. A good upgrade (ie, we might be put in a higher class for no extra charge),

or

2. The other kind (ie, instead of the tickets we request, they'll sell us the most expensive ones instead and bill our card for the difference)?

Thanks.