The amount of RAM that PMOD tries to allocate has been specified and is used for the starting script. To change it, please open the script RunPmod.bat in Pmod4.2/Start in a text editor. It contains lines similar to
.\java\jre\bin\java -Xmx16000M -jar pmod.jar
The -Xmx16000M option specifies the maximum heap memory (16000 MB) that PMOD can allocate. If needed, change the amount and save the modified script.
Note that for processing large data sets it may be necessary to install additional RAM and adjust the starting script accordingly. The assigned memory should be somewhat below the physical RAM of the system.