When we recieve pricing info from your MT4 Server we recieve pricing without markup, so in almost all the cases we need to adjust it.
The easiest way to explain Spread Adjustment Markup is with an examle:
1.23000 <--- Bid
1.23010 <--- Ask
Spread = |bid-ask|
10 <-- Spread
Lets Implement a MARKUP of 1.6
1.6 / 2 * 0.0001 = X
X = 0.00008
Bid - X = 1.22992
Ask + X = 1.23008