Hi @kenji
Sorry for our later reply, as you post the RT question in the wrong community, next time, if you have the RT questions, please post it in this community:
https://community.nxp.com/t5/i-MX-RT/bd-p/imxrt
Now, answer your questions, please read the RM next to your picture, you will find it is clear to understand about the B2B mode:

So, the B2B function is minimize the trigger time, it will trigger will happen immediately after the ADC conversion, if no B2B, the next trigger will have delay. About the detail settings, you can check the ETC_TRIG Chain Register, B2B bit

Wish it helps you!
If you still have questions about it, please kindly let me know.
Best Regards,
Kerry