Number of Products showing on list

This field shows comma delimited numbers in it (4, 2, 8, 12), what do these mean?
Select the Allow customers to select page size checkbox to enable customers to select a page size on the Category Details page from the page sizes list entered by the store owner. In this case, the Page size options field becomes visible in the Administration area. When this option is disabled, customers will not be able to select a page size on the Category Details page and the store owner can enter a certain page size. In this case, the Page size field becomes visible in this case. In the Page size field, enter the number of products to display on the category details page per page. For example, when you add seven products to a category and you set its page size to three. Three products per page will be displayed on this category details page in the public store. (the user guide)


And, can this be set for all categories at once? (same for each manuf page)
No. But you can always create and execute a SQL command which will update page size of all categories at once.

I need to have all my products on the same page, so definitely dont want just 4 showing.
Ensure Allow customers to select page size is unchecked and Page size is set to 1000000

How about changing the default column number from 2 to 3.
I know I can change the VIEW directly but i was wondering if there is a setting somewhere ?

In the Catalog Settings it says:
Allow customers to select 'Products by tag' page size:    
'Products by tag' page. Products per page:

I think 'Products by tag' should be ommited since it applies to all kind of pages

In the Catalog Settings it says:
Allow customers to select 'Products by tag' page size:    
'Products by tag' page. Products per page:

I think 'Products by tag' should be ommited since it applies to all kind of pages
No, it applies only to 'Products by tag' page. Catalog and manufacturer page settings are managed on appropriate category/manufacturer details pages in admin area.