Small enough of a gap not to worry about. It should fill quite easily with whatever finish you plan to use.
Note that the neck does not sit with the tenon touching the rear of the neck pickup rout. The neck needs to be moved back so the end of the fretboard is 0.5mm-1mm beyond the front of the neck pickup rout, just enough so the edge of the pickup ring can sit on it without showing a gap into the rout itself. Otherwise the pickup won’t fit in the rout and the neck will probably be too far back to intonate the strings properly.