The plot variable, Icebox, appears in both the listing and the output. The plotting symbol is 'R'. AXIS= sets the minimum value of the axis to 2500 and the maximum value to 3600. BY 25 specifies that each print position on the axis represents 25 units (in this case, dollars). 
proc timeplot data=sales;
   plot icebox='R' / axis=2500 to 3600 by 25;