How did Starfleet replace 39 ships in a year?

39 starships were destroyed at the Battle of Wolf 359 (Star Trek: The Next Generation, "The Best of Both Worlds, Part 2"). Close to the end of the episode, Commander Shelby moved on from the Enterprise to help rebuild Starfleet. She indicated this would take "less than a year".

Replacing 39 starships and 11,000 people in less than a year seems to be an impossible task, even in the future depicted in Star Trek. Was this estimate just an attempt by Commander Shelby to brag and exaggerate (based on her penchant for greater power within Starfleet)?

In the end, do we have any information indicating how long it did, in fact, take to replace 39 starships?