Add as many as you like and to get that price, use the extra 15% coupon code:
They will give free shipping with or without the coupon, no minimum quantity required from what I can tell.
The coupon can only be used once per account though (not sure if its for new customers).
Normally this goes for $5+ in the stores. My local stores recently raised the price to $6+ for this, so I think a price increase is in the process.
Note that since this is raw/unfiltered, it has the mother of vinegar in the bottle.
I like the taste of this vinegar, and use it on many things. IMO its especially good on fish. It also has a lot of potential health uses/benefits.
Some information on this product is here:
200+ reviews on amazon (including info on a variety of uses and anecdotal stories of how it affected people's health)
Edit: Thanks akrasia for letting me know about the new better 15% off coupon code