¿Por qué es el valor de yy y er1 -1. # IND para este código VHDL? Que esta mal

¿Por qué es el valor de yy y er1 -1. # IND para este código VHDL? ¿Qué pasa?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.math_real.all;
use IEEE.STD_LOGIC_Unsigned.ALL;

use IEEE.NUMERIC_STD.ALL;
entity random is
    generic ( width : integer :=  32; 
    nn:natural:=1; --power of the binomial distribution <16
    m:REAL:=0.0     -- mean output value

    ); 
port (
      clk : in std_logic;
      random_num : out std_logic_vector (width-1 downto 0);   --output vector
      RST : in STD_LOGIC;
      DATA_OUT : out REAL:=0.0            
    );
end random;

architecture Behavioral of random is
        type arri is array (0 to 15) of integer;
        type arrr is array (0 to 15) of real;
        signal noisysignal1:real;
        signal a : integer := 0;
        signal yy : real;
        signal er1 : real;

begin
process(clk,rst)
variable rand_temp : std_logic_vector(width-1 downto 0):=(width-1 => '1',others => '0');
variable temp : std_logic := '0';

 variable s1:arri:=(3,33,333,3,4,5,6,7,8,9,11,22,33,others=>55);
 variable s2:arri:=(5,55,555,50,6,7,8,9,5,6,7,21,33,others=>22);
 variable r:arrr:=(others=>0.0);
 variable s:real:=0.0;

 variable y,er : real;
 variable w1,w2 : real :=0.0;
 variable u : real:= 0.002;

 variable noisysignal:real;

begin
if rst='1' then
DATA_OUT<=0.0;
elsif(rising_edge(clk)) then

temp := rand_temp(width-1) xor rand_temp(width-2);
rand_temp(width-1 downto 1) := rand_temp(width-2 downto 0);
rand_temp(0) := temp;

s:=0.0;
for i in 0 to nn-1 loop    -- nn noise generators
                   UNIFORM (s1(i),s2(i),r(i));
                   s:=s+r(i);
        end loop;
            DATA_OUT <= 2.0*(s/real(nn)-0.5)+ m;
            noisysignal:=real(to_integer(signed(rand_temp)))+( 2.0*(s/real(nn)-0.5)+ m);
            noisysignal1<=noisysignal;
            if(a<1000) then
            y:=noisysignal*w1;--+noisysignal1'last_value * w2;
            yy<=y;
            er:=y-real(to_integer(signed(rand_temp)));
            if(er<0.0)then
               er:=-er;
            end if;
            er1<=er;
            w1:=u*noisysignal1*er+w1;
            w2:=u*noisysignal1'last_value*er+w2;
            a<=a+1;
            end if;

end if;
random_num <= rand_temp;
end process;
end Behavioral;