That's mean, if you have 100 USD, you have to made a several position that will use a 2.5 million of volume in sum. For example if you open 1 position for 100 usd and use of leverage 1:100 that's mean that your position volume is 100 usd*100 = 10 000 usd, or 0.01 million. 250 such positions is 2.5 millions. But also don't forget about a commission and loss positions etc. This system works good if you do a good trading, and multiply your equity.
Please look at this article it explains how to meet a volume requirements: https://www.dukascopy.com/fxcomm/fx-article-contest/?Tips-To-Lower-Commissions-And&action=read&id=2673