If you own physical cartridges, you can dump your own ROMs using a modded 3DS with . This process creates a 100% verified dump because GodMode9 calculates the hash against the cartridge.
In the context of ROM collections, "verified" means that the digital file (usually in .3ds , .cia , or .cci format) is a of the original cartridge or eShop download. Verification is typically conducted using cryptographic hashes (MD5, SHA-1, or CRC32). 3ds rom collection archive verified