Anyone fancy giving me a quick run through?

I know you use something like tink + mystic to do it, and that the max you can combine is 2.6(?) with the formula being something like .. 2.6 + 2.6 - (is it 1 or 2 here?) = outcome

max is 2.6, the equation is x+y-1=final jewel

if x =brace and y=brace then the final jewel will be a brace
if x isnt = y the final jewel is random