Why cannot I allocate more than -Xmx700M

[Sharkie]

last pid:  1526;  load averages:  1.17,  0.90,   
0.47                                                          up  
0+00:09:36  00:31:59
105 processes: 1 running, 104 sleeping
CPU: 10.0% user,  0.0% nice,  1.1% system,  0.0% interrupt, 88.9% idle
Mem: 948M Active, 422M Inact, 126M Wired, 1516K Cache, 112M Buf, 1506M  
Free
Swap: 16G Total, 16G Free

   PID USERNAME  THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU  
COMMAND
  1500 root       56  49    0   904M   552M ucond  5   0:06 77.20% java
   757 mysql      12   4    0  1156M   436M sbwait 1   0:26 15.72%  
mysqld


My machine does have more than 700M available when I try to start my  
Java app, but I could only do at most 700M.

Is there an artificial limit or something that I cannot see here? I  
have 1506M remaining, which I cannot use in this single java app?

However, if I launch 5 Java app each getting 300M heap, then I have no  
problem.

It's really odd.

Is there a way I can override FreeBSD and assign to this Java app all  
that I think it deserve?