There were likely many (e.g. maybe even 100s) times more documents written that didn't. Considering the survival rates of books (so if we entirely ignore various non-litterar documents) written in the Roman Empire during its more stable periods that wouldn't be far fetched at all.
e.g. we know that Carthage or other Phoenicians cities, Etruscans etc. were highly literate, the fact that effectively all written content from those civilizations was destroyed or lost doesn't change that much.
There was effectively a bottleneck in early medieval Europe if a given text survived until the Carolingian period or 900-1000 AD the likelihood of it surviving was reasonably high.
There were likely many (e.g. maybe even 100s) times more documents written that didn't. Considering the survival rates of books (so if we entirely ignore various non-litterar documents) written in the Roman Empire during its more stable periods that wouldn't be far fetched at all.
e.g. we know that Carthage or other Phoenicians cities, Etruscans etc. were highly literate, the fact that effectively all written content from those civilizations was destroyed or lost doesn't change that much.
There was effectively a bottleneck in early medieval Europe if a given text survived until the Carolingian period or 900-1000 AD the likelihood of it surviving was reasonably high.