The Security of AES-N-GCM
You appear to have computed things correctly. However, you have quoted their Corollary 1 wrong: you've included an extra $-q^22^{-128}$ term in the confidentiality part  (don't know if that was what confused you though). To get their $2^{-89.4}$ instead of your $2^{-89.5}$ simply include more decimals of $\log_2(95)$.