If you want to verify what the heap size is set to you can follow these steps:
Enable basic logging and it shows up in the java console.
Java Web Start 10.25.2.17
Using JRE version 1.7.0_25-b17 Java HotSpot(TM) 64-Bit Server VM
User home directory = C:\Users\i808638
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c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
0-5: set trace level to <n>
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basic: Java part started
basic: jnlpx.jvm: C:\Program Files\Java\jre7\bin\javaw.exe
basic: jnlpx.splashport: 52750
basic: jnlpx.remove: true
basic: jnlpx.heapsize: 67108864,134217728
network: Loading user-defined proxy configuration ...
network: Done.
network: Browser is null
network: Browser is IE
Regards,
Sam