It's already explained. See my post above.
#15
This is actually mathematical.
Freewill at the end means one is given the ability to oppose God.
By assuming a normal distribution (i.e., mathematical statistics and probabilities) of human or angel behavior by free will, it's estimated that 1/3 angels will choose to sin against God when measured by Law. Since humans are given a larger degree of freewill. It is estimated that more than 2/3 humans will choose to sin against God when measured by the same Law. Humans are thus said to be saved through the narrow gate.
However another factor jammed in besides the freewill factor. The 1/3 bad angels (crafty snake in Eden) are much more intelligent than humans and can pose a negative effect upon humans. As a result of the angelic influence, it is said that Satan kept all humans under captive. That is by freewill alone there shall be 1/3 or less humans are deemed savable, but with the angelic influence in place no human can be saved. After extended observation and witness, Law would enforce the destruction of humankind as a whole (that is what the Noah story told).
With Jesus Christ in place then, humans can dodge the Judgment of Law. That is, human behavior are no longer measured by the standard as defined by Law. Instead they are assessed by means of a series of covenants covering the different scope of humans at the various points of humanity.
While Law actually assesses the obedience of an entity with freewill, covenants would assess Faith which is equally crucial to humans for them to live with the eternal God (as told by the Eden story where Adam fell because of the lacking of faith in God and lacking obedience at the same time). A covenant thus would assess both Faith and obedience, and with the New Covenant only assesses a human's Faith and faith only, as both the saved and unsaved are equally inobedient that any form of Law won't be able to tell them apart. Only faith would indicate who can live the sin-incompatible God in the forever realm.
The math,
Freewill alone:
2/3 angels saved by means of a Judgment of Law, 1/3 or less humans are saved in the same way.
But with influence from angels:
zero humans are saved.
With Jesus' self-sacrifice:
1/3 or less humans will be saved by means of a Judgment of Covenant.
Promise from the completely sin-incompatible God,
If angels passed the Judgment of Law or humans passed the Judgment of Covenant, God would bear with them in eternity no matter what (as a Shepherd to His sheep).