Ahk gui does not display double digit numbers

Question

I’m trying to make the GUI window add a number when you click F7, when you click it displays a new number one more, but it only goes up to 9, then it starts showing all the numbers without 0, although the script itself writes more than 10, I checked it via send

chis:=!chis
chis = 0

F6::
Gui, +LastFound +AlwaysOnTop -caption +ToolWindow
Gui, add, text, cGreen, Myasnoy den
Gui, add, text, vStatus, %chis%
Gui, Show, restore w150 h80 x1750 y580 NoActivate, window
return

F7::
IfWinNotExist, window
{
     Gui, Destroy
     return
}
GuiControl,,Status, %chis%
chis++
Send, only chis %chis%
return

I expected that the GUI window would be displayed after 9 and then 10,11,12,13 (and not 1,2,3)