John Calvin 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 also Jesus did. If the Evangelist had not cautioned his readers with this observation, they might have supposed that he had left out none of the miracles which Christ had performed, and had given a full and complete account of all that happened. John, therefore, testifies, first, that he has related only some things out of a large number; not that the others were unworthy of being recorded, but because these were sufficient to edify faith.

And yet, it does not follow that they were performed in vain, for they profited that age. Secondly, though today we do not have detailed knowledge of them, still we must not suppose it to be of little importance for us to know that the Gospel was sealed by a vast number of miracles.