Update Custom-Output.md

Author: talbring

_docs/Custom-Output.md

@@ -66,7 +66,7 @@ For the compressible Navier-Stokes solver (i.e. `PHYSICAL_PROBLEM=NAVIER_STOKES`
 |  `FORCE-Z` | Total Force in z direction.|  `AERO_COEFF`  |
 |  `EFFICIENCY` | Total Lift-to-drag ratio. |  `AERO_COEFF`  |
 
-## Volume Output ##
+## Customizing the volume Output ##
 
 The `VOLUME_OUTPUT` option can be used to set fields for the restart and visualization files. Here you have the option to specify either single fields and/or groups.