How can Toudou Kirin be ranked 1 if Claudia is undefeated? In episode 6, it was shown that Claudia Enfield is the 2nd rank. However, Julis-Alexia von Riessfeld said that Claudia is undefeated.

So, how can Toudou Kirin be ranked 1 if she never defeated Claudia?
I just watched this series a few days ago, Kirin is rank 1 because of overall combat ability being ranked higher due to 2 things:


Kirin is not a strega
Kirin does not use a lux in battle (at least before she fought Ayato)


Because of that, even though Claudia is undefeated, in terms of strength Kirin is viewed as stronger. 

This gets discussed in a later episode of season 1, though I'm not sure which one exactly.

Edit 

Just to clarify, Kirin does end up getting a lux later in the novel but it isn't shown in either of the anime seasons. She uses a normal katana