Corrected viper int range to -2**31 to 2**31-1

Improving-performance-with-Viper-code.md

@@ -35,7 +35,7 @@ add_to_array( my_array, 10 )
 viper_add_to_array( my_array, 10, len(my_array) )
 
 ```
-This viper function is about 16 times faster on my ESP32-S3 with PSRAM wih an array of 10000. 
+This viper function is about 16 times faster on a ESP32-S3 with PSRAM wih an array of 10000. 
 
 In this example, the original add_to_array() function with @micropython.native decorator is about 1.6 times faster than the original function.
 
@@ -109,7 +109,7 @@ In case you are familiar with C: The viper data types are similar to some C lang
 
 ## The viper int data type
 
-The viper ```int```data type in viper code is a special data type for fast signed integer operations. A viper `int` can hold values from -2\*\*31-1 to 2\*\*31, i.e. this is a 32 bit signed integer.
+The viper ```int```data type in viper code is a special data type for fast signed integer operations. A viper `int` can hold values from -2\*\*31 to 2\*\*31-1, i.e. this is a 32 bit signed integer.
 
 A viper `int` is different to the ```int``` we know in MicroPython, which is still available in viper decorated functions as  ```builtins.int```.  Hence this document will make a difference between a "viper ```int``` opposed to a ```builtins.int```.