How do I calculate the size of data files of SMARTDAC+ GX/GP series?

Files consist of "information other than sampled data," and "sampled data."

For details on calculations, see the user's manual (IM 04L51B01-01EN)
◊Appendix 1, "File Size of Display Data and Event Data."
User's Manual (IM 04L51B01-01EN)