Decimal places using RTOS or should I use something else ?

Hello, I have a small problem with decimal places.

I have written a small program to write an altitude and draw small figure.

Example :

when "z" value is 3.0931456... it turns into 3.093 (OK, 3 decimal places)

But if "z" value is 2.0000000... it turns into 2 (NOT OK, 0 decimal places), Must be 10.000

Using this command:

(setq alti (rtos alta 2 3))

See here: Consistent rtos

when Z = a string:

(setq alti "2.00000000") <= given value
(setq alti (strcat (substr alti 1 (vl-string-position (ascii ".") alti)) (substr alti (+ (vl-string-position (ascii ".") alti) 1) 4)))
returns: "2.000"

when Z = a real:

(setq alti 2.00000000) <= given value
(setq alti (rtos alti))(setq alti (strcat (substr alti 1 (vl-string-position (ascii ".") alti)) (substr alti (+ (vl-string-position (ascii ".") alti) 1) 4)))
returns: "2.000"

; =========================================================================================== ;
; Konwertuje liczbe na lancuch tekstowy / Converts number to a string                         ;
;  Val  [REAL/INT] - liczba do konwersji / conversion number                                  ;
;  Unit [iNT/nil]  - jednostki wyjsciowe / output unit                                        ;
;                    nil = domyslne / default | (getvar "LUNITS")                             ;
;                    1   = naukowe / scientific                                               ;
;                    2   = dziesietne / decimal                                               ;
;                    3   = inzynierskie / engineering                                         ;
;                    4   = architektoniczne / architectural                                   ;
;                    5   = ulamkowe / fractional                                              ;
;  Prec [iNT/nil]  - INT = liczba miejsc po przecinku / number of decimal places              ;
;                    nil = domyslna / default | (getvar "LUPREC")                             ;
; ------------------------------------------------------------------------------------------- ;
; (cd:CON_Real2Str 12 2 4)                                                                    ;
; =========================================================================================== ;
(defun cd:CON_Real2Str (Val Unit Prec / DMZ res)
 (setq DMZ (getvar "DIMZIN"))
 (setvar "DIMZIN"
   (if (not (member (getvar "LUNITS") (list 4 5)))
     (logand DMZ (~ ) 0
   )
 )
 (setq res
   (rtos
     Val
     (if (and Unit (member Unit (list 1 2 3 4 5))) 
       Unit
       (getvar "LUNITS")
     )
     (if Prec Prec (getvar "LUPREC"))
   )
 )
 (setvar "DIMZIN" DMZ)
 res
)

From: CADPL-Pack-v1.lsp