ok. i understood the problem . we will shift the "-" string 1 step left.

change the "ekran_0" label with below ;

Code:
ekran_0 :  ; transfer the registers to diplay
    
    mask_3 = isi dig 3
    
    if sign = 1 then 
        mask_3 = "-"
    endif
    
    mask_2 = isi dig 2
    mask_1 = isi dig 1
    mask_0 = isi dig 0

return