Update readme.md

Author: javadev

src/main/java/g2001_2100/s2011_final_value_of_variable_after_performing_operations/readme.md

@@ -57,9 +57,11 @@ X++: X is incremented by 1, X = 0 + 1 = 1.
 
 ++X: X is incremented by 1, X = 1 + 1 = 2.
 
---X: X is decremented by 1, X = 2 - 1 = 1. X--: X is decremented by 1, X = 1 - 1 = 0.
+--X: X is decremented by 1, X = 2 - 1 = 1.
+
+X--: X is decremented by 1, X = 1 - 1 = 0.
 
 **Constraints:**
 
 * `1 <= operations.length <= 100`
-* `operations[i]` will be either `"++X"`, `"X++"`, `"--X"`, or `"X--"`.
+* `operations[i]` will be either `"++X"`, `"X++"`, `"--X"`, or `"X--"`.