The article 114(C) (C) Temperature Limitations.it is a little confusing:
The temperature rating associated with the ampacity of a conductor shall be selected
(C) Temperature Limitations. The temperature rating associated
with the ampacity of a conductor shall be selected
and coordinated so as not to exceed the lowest temperature
rating of any connected termination, conductor, or device.
Conductors with temperature ratings higher than specified
for terminations shall be permitted to be used for ampacity
adjustment, correction, or both.
310.15 Ampacities for Conductors Rated 0–2000 Volts (B) Tables:
The temperature correction and adjustment factors shall
be permitted to be applied to the ampacity for the temperature
rating of the conductor, if the corrected and adjusted
ampacity does not exceed the ampacity for the temperature
rating of the termination in accordance with the provisions
of 110.14(C).
For instance let's take 1/0 copper conductor 90oC insulated
From Table 310.15(B)(16) I=170 A for 3 conductor per position
Now let's take 6 conductors from Table 310.15(B)(3)(a)
I=170*.8=136 A
From Table 310.15(B)(16) I=150 A for 75oC
That means since 136<150 A it is permitted.