Some variables are not clarified in the paper

[The-kamisato-Sii]

I have been following your valuable work and have gone through your code. However, I noticed that some variables, such as "regrets," are not explained in the paper. I was wondering if these are terminologies from previous work that I might not have come across yet. Could you please provide the relevant references or the code you referred to for this part? I believe it would be very helpful for me, and I'm eagerly looking forward to and appreciative of your valuable response!