Updated macro API documentation

Author: danieljvickers

docs/documentation/gpuParallelization.md

@@ -44,14 +44,16 @@ Note: Ordering is not guaranteed or stable, so use key-value pairing when using
 
 **Macro Invocation**
 
-Uses FYPP eval directive using `#:call`
+In order to parallelize a loop, simply place two macro calls on either end of the loop:
 
 ```C
-#:call GPU_PARALLEL_LOOP(...)
+$:$GPU_PARALLEL_LOOP(...)
    {code}
-#:endcall GPU_PARALLEL_LOOP
+$:END_GPU_PARALLEL_LOOP()
 ```
 
+This wraps the lines in `code` with parallelization calls to openACC or openMP, depending on environement and compiler settings.
+
 **Parameters**
 
 | name             | data type           | Default Value     | description                                                                               |