A.T. Robertson Commentary John 20:30

"Many other signs therefore did Jesus in the presence of the disciples, which are not written in this book:" — John 20:30 (ASV)

Many other signs (πολλα αλλα σημεια). Not only those described in the Synoptic Gospels or referred to in general statements, but many alluded to in John's Gospel (2:23; 4:45; 12:37).

Are not written (ουκ εστιν γεγραμμενα). Periphrastic perfect passive indicative of γραφω, do not stand written, are not described "in this book." John has made a selection of the vast number wrought by Jesus "in the presence of the disciples" (ενωπιον των μαθητων), common idiom in Luke, not in Mark and Matthew, and by John elsewhere only in 1 John 3:22. John's book is written with a purpose which he states.