"So when A seed bank Say's A Plant Will Produce 300 Gram Per m2."
On average, (typically indoor cultivation ratio) meaning how many grams the plant will produce in a Meter squared. (10.763 square feet or an area of about 3.2' X 3.2')
If a plant is capable of 300 Grams Per Meter Squared, it is like saying it is possible to produce 10.5 Ounces in a 3.2' X 3.2' area..
3.2' = 3.2 feet
3.2" = 3.2 inches
LOL = Laughs out loud.