Question about Product Prices and Attributes

I am a bit confused with inputting products and prices. I am inputting products (ink bottles), which will be available in 3 sizes: 1oz, 2oz and 4oz. I created the attributes for this and selected them for each product. How do I input the correct pricing? On the product input page I select: 'Product Priced by Attributes'.... yes....
In Tax class I select: Taxable Goods...
In 'Products Price(Net) I input what exactly? The price for the 1oz bottle as a base for the other sizes? Leave it blank and just input the prices in the Attribute page? What is the correct way of doing this? I read up on this subject but couldn't get a clear answer.

Also... the box 'Products Quantity', right above "Products Model"... what does that refer to? The amount that will be shipped by default for a product? The stock amount available?

Thank you for your assistance.
Yolanda

If you mark the Product as Priced by Attribute you would enter for the Product Price: 0.00

Then, you would add the full individual price to each Attribute and remove the Prefix of the +/- ...

'Products Quantity' is number in stock.

Thank you both for your reply. That's what I have been doing but you confirmed it. Much obliged for the help.

Yolanda