Appropriate "title" to list on application for professors writing LOR?

In filling out my very first grad school application I've come across the Letters of Recommendation page. It says to list the "Title" of the recommender. Do I use Professor here? Or Dr.? I am stumped. Both of my recommenders are professors and that is how I refer to them, but I am just not sure which one I should be putting here since they have Doctorate degrees. I don’t want to make a mistake. I found this question which was sort of related, but also confused me even more. If the professor has a title like X-Y Professor of Z or Professor of X and Y, do I use that full title? Or should I just write "Professor" or "Professor of [subject]"?

Another thing I should mention is that below, there is a dropdown list of options for "Relationship to you" and in there it says professor as an option. So this might lead me to think that I should list their full title as a professor rather than just "professor" or "Dr.," am I correct in thinking this? (However, I just tried typing the whole thing and it wouldn't fit.)

I've started using "Required Title" whenever I'm asked for my own title. (And for "relationship to the applicant" I always write "see letter".)