10% of Medieval Manuscripts survive to this day - Is that an overestimate?

[Scarecrow]

The chances of old manuscripts surviving, depended on many things, mostly on their type and their subject matter, but also where it was made. Religious and liturgical texts have the highest rates of preservation, owing to their sacred significance and the deliberate care taken to protect them. In contrast, secular writings, personal documents, and practical manuals tend to have much lower survival rates. 

It is estimated that scientific manuscripts like herbals, medicine, and other natural sciences, but also alchemy, had a moderate chance of surviving. They were valuable for learning and passed around among scholars and healers. Their survival rate is better than letters, manuals and stories.but less than religious matter.

So while 10% is general estimate, class survival rates can differ quite a bit.