I would say even less than 10%, but we are in basic agreement on the fact it was much less than what the Russians needed. The Ukrainians were stronger than the Russians estimated, and the Russians were weaker than anyone knew. This caused them to go in with less than they needed.
The question is how were we all so wrong about it.
It had about the same number of soldiers as France, Germany, UK, Italy, and Turkey each have, and about twice as many troops in Europe as the USA. But numbers are not everything. In terms of equipment and training, there are many other armies that were stronger than Ukraine. Both France and the UK have nuclear weapons of their own. That is a power that Ukraine just does not have.