Can a non compete be part of an installment sale 6252

Can a non compete be part of a installment sale or should it be not attached to  form 6252?  I entered it as a an asset held for less than one year so it will be short term CG.  But when linked to the installment sale I am showing almost a $1100 less in the federal tax owed on a $5000 dollar non compete clause compared to when not linking it to the 6252 owing the $1100...  Something is not adding up so Im guessing it cannot be linked?