[enscr]

If you analyse it as probability it makes a lot more sense than intuitively thinking about it. A login & a password combination can also be seen as a unique string combination and so is 2FA i.e. a 3 string combination. Not really multiple levels of security mathematically.

[sp332]

With 2FA, the string changes each time you log in.

[enscr]

There's a finite probability of landing on the combination of login+password+2FA-string at any given instance.

[Bootvis]

Finite and positive ;)