When you get any item, it gives you a message in the top left on what it does. You can even check the console if you missed it. The Ammo Digitizer gives you 3x ammo from any ammo pickups. You can spam beam combos on RVZ1's enemy hordes and still get more ammo than you lost.
It's a miracle chance, but you can make it guaranteed if you find out how to lit all 4 lights at the top of your visor.
Did you mash through the first-setup menu? It asked you if Samus should auto-add music. If you go to the SRB2 folder, then into luafiles>client>metroidvanguard and delete firstsetup.dat, you can go through it again and see it for yourself.
This is how you know somebody hasn't really fought the custom bosses or completed a 5% run. :P
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Metroid Vanguard 1.1 is now out! It features quality of life changes, balance adjustments, bugfixes, and an in-level warning in ACZ4 with the option to hide a scene for those sensitive to intense violence!
Changelog and download in the release post!