Simulating in EdaPlayground the following code,
gives me the simulation results below the code

--CONCURRENT PROCEDURE CALL TIMING PROBLEM
ENTITY tb IS
END ENTITY tb;

ARCHITECTURE sim OF tb IS
  SIGNAL cnt  : integer RANGE 0 TO 3 := 0;
  SIGNAL str  : string(1 TO 5) := (OTHERS => ' ');
 
  PROCEDURE test (CONSTANT number  : IN integer RANGE 0 TO 3 := 0;
                  SIGNAL   num_str : OUT string(1 TO 5)) IS
  BEGIN
 
  
    CASE number IS
      WHEN 0      => num_str <= "zero "; REPORT "Zero";
      WHEN OTHERS => num_str <= "one  "; REPORT "One";
    END CASE;
  END PROCEDURE;
  
BEGIN
  test(cnt, str);  -- CONCURRENT CALL TO PROCEDURE TEST
  
 PROCESS 
 BEGIN
 
  
  FOR i IN 0 TO 3 LOOP
    WAIT FOR 10 ns;   --this timing is not OK. Second transaction is @20ns WHY not @10ns
     cnt <= i;
     --WAIT FOR 10 ns;  --this timing is OK
  END LOOP;
 WAIT;
 END PROCESS;
 
 ----Process
-- begin
 --wait until cnt'transaction;
 --report "*******************Transaction happen at report current time = " & time'image(now);
 --end process;
 
END ARCHITECTURE sim;

My question is, why simulation Time advances 0ns,20ns, 30ns, 40ns and not
0ns, 10ns, 20ns, 30ns ?
If i move the ‘WAIT FOR 10 ns;’ after cnt <=i; simulation timing looks correct.
Is it some sort of race condition?