Confused about payment/term differences between ICR & IBR

I got an email that I need to manually recertify my information for IDR so I am in the process of doing that now. The online process is now asking me to choose between IBR and ICR. I am confused about why it’s giving me a higher payment for IBR vs ICR and why the “End of Term Date” is different between the plans.

For context:

– Outstanding balance: $27,000

– New household AGI: $97,500

– Live in Missouri

– Currently on ICR, payment is $273

– Loans are all from 2015-2019

The website is showing me a Standard Repayment monthly amount of $317 with end of term date 9/2034, IBR at $290 ending 8/2035, and ICR at $258 ending 11/2036.

So why is IBR higher than ICR? And do they all have different dates just because of the payment amounts, so I will pay off the loans slower with ICR? Also, my recertification date on the dashboard isn’t until August of this year so I’m not sure why I was notified now; is there any benefit to waiting until later in the year to recertify and choose the plan? If I recertified today, would the higher payments start now or on that later date?

Thanks in advance for any help!