I received this question, and thought it might be of general interest. In fact, I had to look up the answer myself, just to be sure:

"I was wondering when using the MLSN Guidelines how to calculate how much of a specific nutrient you are applying in a liquid fertilizer?"

I replied:

In a liquid fertilizer that is pre-mixed, I think the % given is by mass, and not by volume. So you need to take that % and then correct for it based on the density of the particular fertilizer you are using. That info should be on the label, lbs/gallon or whatever, and then you make the conversion to figure out how much you are putting out per unit area of turf.

Method explained here:

https://pubs.ext.vt.edu/424/424-035/424-035.html

Look at this Grigg Bros product, for example:

http://www.griggbros.com/products/proven-foliar/ultraplex

It is 0.4% manganese by weight. And 1 gallon of this fertilizer is 10.68 lbs. So if you apply at the 6 oz/1000 rate, that is going to be (this is where I remember how convenient metric is!):

128 fluid ounces in 1 gallon, so 128 fluid ounces is 10.68 pounds

10.68 / 128 = 0.083 lbs of product per 1 fluid oz

0.083 * 6 = 0.498 lbs of product (I'll round up to 0.5) going down per 1000 ft²

For the manganese rate, it would be 0.5 lbs * 0.004 = 0.002 lbs Mn/1000ft²

Out of curiosity, the N (4% in this product) at the 6 oz rate would be 0.5 * 0.04 = 0.02 lbs N / 1000