All array entries must be positive integers, % = unchanged part of array
[a] = a
[a,%] = a^(3*[%]+3)
[10,1] = 10^(3*1+3) = 10^(3+3) = 10^6 = million
[10,10,1] = 10^(3*[10,1]+3) = 10^(3*10^6+3) = 10^(3,000,003) = millillion
[10,10,10,10,42] = ... = 10^(3*10^(3*10^(3*10^42+3)+3)+3) ~ multillion
[10,10,10,10,10,9] = 10^(3*10^(3*10^(3*10^3*(10^9)+3)+3)+3) = short-scale bentrizillion
The limit of this notation is [n,n,n...n,n,n], repeated n times. This only reaches omega on the fast-growing hierarchy.
You can add L before the array and rule 2 changes to L[a,%] = a^(6*L[%]) which lets you make long-scale illions.
L[10,10,10,10,10,12] = bentrizillion