I bought some Stihl HP Ultra for the first time today. I got a 6/pk of their "2.5 gal" bottles which are supposed to have 6.4 oz. in them. However, according to the scale on the side of the bottle, there is more than 6.4 oz. in there, they are more like "6.9-7". So which is it, is the bottle scale right, or is there 6.4 oz. there? I'm making up 1 gallon so I needed to measure out approximately 2.6 oz.