How Do I Change the Photo ID Number Sequence

I want to change the sequence of the photo ID numbers. As I’m building a gallery I had to delete a bunch of pictures and there is a large gap in the numbers, because when I upload new images they just keep numbering from the highest one which I had deleted. I think this has to be done in the database, in the nggpictures table.

There is a column for “pid” and it is set to auto increment, but when I enter a new default value it says incorrect value for default, and I can’t turn off auto increment. I want to enter my own starting number for the next uploaded image.

Does anyone know how I can do this?