First off, the devil's in the details of reporting. The 355 ship navy is a cap / target is on specifically manned warships that kill and blow up things. The 530 ship Navy includes support / logistics, command, and unmanned ships, which our current fleet sits at 490. This isn't really a big jump, and the study even recommends decommissioning some warships in our fleet including two carriers.
If we're including tankers, logistics, command, tenders, repair, and salvage ships, then 500 isn't nearly enough. Right now we have 130 USNS ships, 14 maritime prepositioning ships, and 290 war ships. That's a current total of 434 ships which can barely meet our current operational needs and we're going to add 66 new ships and think we can sustain a large scale fleet engagement with a peer adversary? That's laughable.
During WW2 we built 860 auxiliary ships of various classes and descriptions to support, repair, and salvage the fleet. We literally had thousands of these ships to support about 800 warships and submarines and keep the fight going. There is no possible way we can maintain a protracted, full scale war with just 500 ships spanning both ships of the line and auxiliaries. No matter how you look at it, this study seems like nonsense.