OK, if you have a digital scale and MG is also a dry(powder) nutrient, you will be able to come up with the correct proportions:
Say you mix 1 part Mg and 1 part ammonium N, 1 part, meaning equal weights of each, your N-P-K
will be : N = 22 = (34+10)/2
P = 5 = (0+10)/2
K= 5 = (0+10)/2
So, 22-5-5
which is a little off balance.
Can you see the math behind this? How I am figuring out the N-P-K values?
So, the 10-10-10 is O.K. as a standalone, if it also has the micros. The Ammo Nitrate is only gravy, and should, at most be added at 1 part Ammo Nitrate to 4 parts MG.
This will give you an N-P-K of appx 15-8-8. A little off balance with the K, yet, but is adequate. Not ideal, however.
No matter what amount of N you add, I highly recommend a K supplement. Guess what? I sell that too! It's a product called "K Bomb."
Sorry for the shameless plugs. I see a need here.