Where do I find default value for contextual view filters?

Question

I'm finding the views in 7 to be much more confusing than in 6! I'm trying to create a block that will filter by the node ID of the page the block is embedded in. When I look at the help for Contextual Filters in the block display, it says this:

Block displays have no source of contextual filters at all; they cannot pull contextual filters from the URL, and often require use of PHP code as a default contextual filter. Various default values can be applied against contextual filters to use filters in a block view. See "Provide default value," under "When the filter value is NOT in the URL" below.

When the filter value is NOT in the URL

Display all results for the specified field If this option is selected, the contextual filter is removed from the view as though it weren't there and all results will be displayed.

My question is, where do I find these choices for default values? When I click on the Add button next to Contextual Filters, I get a dropdown list of all content fields, not a list of options like "Display all results for the specified field".

Edited to add

The Default contextual filter selection is available only if the action to take is "Provide default value" under "When the filter value is NOT in the URL." When that option is selected, a new fieldset will appear that will allow you to choose default contextual filters. Views provides the following default selectors by default

So where is the "When the filter value is NOT in the URL" choice?

Answer 1

You choose a field from that drop down, and the settings you are talking about come up for that field.

These settings are tied to each field, so you can set different fields to come from different sources with different responses if they're not there.