Depending on what analyzer ...

Depending on what analyzer or lab test you are using, one definition of 'total ammonia' is sum of the monochloramine concentration (in mg/L as N ) + the free ammonia concentration (mg/L as N). Since monochloramine is typically expressed in mg/L of Cl2, total ammonia is a means of tracking the total amount of nitrogen a utility is putting out into their distribution system, and can ultimately help if there are issues with excess biofilm growth, chlorine demand/residual loss or nitrification in the distribution system. 

It should be noted that another common definition of total ammonia is the sum of ionized ammonia, aka ammonium (NH3+) and unionized ammonia (NH3). Some methods of analysis covert all of the species to the same form before analysis. The proportions of ammonia in water existing in either of these states depends on the pH of the water. I presumed it's the monochloramine-focused definition you were looking for since you're chloraminating.