What does the ( not -ant) in the title mean, or refer to?

-ant is seen in the present participle. You can use it to form things that look like -ing but they aren't serving as infinitives. Je fais l'exercice en nageant. == I exercise by swimming. When you work with the infitive you just use the -er, -ir, -re form of the verb and not the present participle. Here's some more information - https://www.laits.utexas.edu/tex/gr/vpp1.html

Thank you.