How much feed is equilvelnt to this?

i am moving my horse on sunday, and the woman doesn't use the plastic scoop she uses one of the metal ones,a href="http://www.collectibles-articles.com/antique/collectible-image-large/vintage-farm-feed-scoop-galvanized-metal-12-1-2-x-7_270674543194.jpg" rel="nofollow"http://www.collectibles-articles.com/ant…/a like this one, my current barn owner uses a plastic scoop like this one a href="http://www.thevetshed.com.au/images/products/NTebhtcGCM-1.jpg" rel="nofollow"http://www.thevetshed.com.au/images/prod…/a currently my horse gets 1 scoop of equine senior and 1 scoop of safe choice in the morning, with 1 scoop of her U-Gard and 1 scoop of her mare magic and 2 flakes of hay, at lunch she gets 1 scoop of safe choice and 2 flakes hay if all her hay is gone from her bag,and if its not she only gets one flake hay, then ad dinner she gets 1 scoop senior and 1 scoop of safe choice and 2 flakes of hay. at the new barn, the woman feeds the same grain to all her horses, its a mix that she and her husband mix themselves, its got safe choice, and its really similar to a 12% feed. and they get that 2X a day then they get 2 flakes of hay at breakfast, if they are out side then they don't get their afternoon hay, then at dinner they get 2 more flakes. so my question is how much feed from the plastic scoop is equivalent to the metal scoop?