Found the following hamletworks.org entries referring to line 673-4

View Commentary Note for 664
664 Ham. It {waues} <wafts> me still,1.4.79
664 Goe on, Ile followe thee.1.4.79

View Immaterial Textual Note for 673-674
673-4 I say away, goe on, Ile followe thee. | {Exit } <Exeunt.>Ghost and Hamlet. 

View Material Textual Note for 673-674
673-4 I say away, goe on, Ile followe thee. | {Exit } <Exeunt.>Ghost and Hamlet. 

View Commentary Note for 673
673-4 I say away, goe on, Ile followe thee. | {Exit } <Exeunt.>Ghost and Hamlet.