The System only had 2, and the other one blew up. It's not impossible they had a third, at the very least some of those Liberator style fighter craft they had may have still been knocking about.
The space battle in Space Fall indicated there were a couple at least, and given if DSV1 had survived (or even been there) they would've tried to have salvaged DSV2 but didn't. It's likely implied DSV2 engaged some other species with a handful of warships in a 'battle group', possibly like the ones seen in Redemption, and all were lost save for the Liberator.
We don't know the full extent of the System's fleet, and given Starworld was destroyed (or otherwise seriously munted) by Orac in Redemption we'll probably never know.