fix

plugins/org.polarsys.chess.mobius/src/org/polarsys/chess/mobius/utils/TransformationUtil.java

@@ -724,7 +724,12 @@ public List<NamedElement> getOrderedAttacksAndFragments(Interaction scenario) {
 	
 	//this assumes that index starts at 0
 	public Integer getAltOffset(Integer index, Integer size){
-		return  (index - size/2)*OFFSET;
+		Integer result = (index +1 - size/2)*OFFSET; //size is even
+		if(size % 2 != 0){ //size is odd
+			result = (index - size/2)*OFFSET;
+		}
+//		System.out.println(result);
+		return result;
 	}
 	
 	public Message getOperandAttack(InteractionOperand operand){