The distinction to me is whether the Bible "is" the Word of God or "contains" or "communicates" the Word of God. "Is," which seems to be the prevailing (and, IMO, unsustainable) view, implies "everything, cover to cover, The Book." "Contains" or "communicates" requires no particular percentage. Much of the Bible is not - simply cannot be - literally true, much is historically false, and much reflects primitive understandings consistent with what other primitive cultures believed. Every scholar knows this, but a curiously large segment of believers think that pretending otherwise is somehow more pleasing to God or more indicative of real faith.
I would say that the 20% (a completely arbitrary number) I assign to profound spiritual truth is 100% of what God actually intended to communicate.