I'm not a PIN number fan/ser, i'll prefer to use the Pin Name instead
Code:
SEROUT PORTB.0,N2400,["Hertz: ",#W1,13,10]
OR using a alias
Code:
SerialOutput    VAR PORTB.0
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SEROUT SerialOutput,N2400,["Hertz: ",#W1,13,10]
You can find an explanation on pin number in section 4.11 of the manual.

HTH