Wrong #defined calculated value

[programandala.net]

I think there's something I'm missing about the way #define values are calculated, look:

Code:

#define screenFirstCol 0 #define screenLastCol 31 #define borderFirstCol screenFirstCol #define borderLastCol screenLastCol #define oWinFirstCol borderFirstCol+1 #define oWinLastCol borderLastCol-1 ' Wrong result, 32 instead of 30: #define oWinWidth oWinLastCol-oWinFirstCol+1 cls print "Expected values in cramps:" print print "screenFirstCol(0)=";screenFirstCol print "screenLastCol(31)=";screenLastCol print "borderFirstCol(0)=";borderFirstCol print "borderLastCol(31)=";borderLastCol print "oWinFirstCol(1)=";oWinFirstCol print "oWinLastCol(30)=";oWinLastCol ' Wrong result, 32 instead of 30: print "oWinWidth(30)=";oWinWidth pause 0 stop

What's the problem?

I think #defined values are simple labels calculated by the preprocessor. Is it right? Is there any limit about the depth of the calculated values?