You don't need to worry about the S::Startup function unless you are calling the (command) function.
Also, you need a leading zero when specifying a real number (in your tspacefac setvar)
This should do it.
Code:
;;ACADDOC.LSP
(vl-load-com)
(SETVAR "LAYEREVAL" 0)
(SETVAR "MIRRTEXT" 0)
(SETVAR "UCSICON" 0)
(SETVAR "TSPACEFAC" 0.8125)
(SETVAR "DIMASSOC" 2)
(vlr-editor-reactor nil '((:VLR-sysVarChanged . VTF)))
(defun VTF (CALL CALLBACK)
(if (= (strcase (car CALLBACK)) "SAVETIME")
(progn
(setq ALK (getvar "savetime"))
(if (/= ALK 5)
(progn
(alert "Savetime has been changed, Resetting to 5 minutes! "
)
(setvar "savetime" 5)
)
)
)
)
)