Mine are only off by about 4 for all of April... My "First Launches" are only 4 higher than my Visits at Visit Number = 1.
I suspect this might be some issue with maybe the app crashing when trying to open the first time? Maybe the First Launch fired, but the Visit didn't get calculated for some reason...
I can't see your data, but are you really saying that "Visits with Visit Number = 1" is 99% higher than your First Launches metric? That sounds like your Lifecycle metrics may not be properly firing.... Have you tested your app? You should see the Lifecycle metrics being triggered as their own call, generally the first call upon opening the app...
This will send your Lifecycle Metrics like "LaunchEvent" (Launches in Workspace), "CrashEvent" (Crashes in Workspace), "UpgradeEvent" (Upgrades in Workspace), and of course "InstallEvent" (First Launches in Workspace).
Whether you are testing via a proxy like Charles or Fiddler, or using AEP Assurance (aka Griffon), you should be able to see all this information being sent to Adobe...