This is a bit too complex to answer in a forum post, but there are good explanations on the TP website.
https://www.trainingpeaks.com/learn/articles/an-introduction-to-trainingpeaks-metrics/
https://www.trainingpeaks.com/learn/articles/training-with-tss-vs-hrtss-whats-the-difference/
What you are calling a “desginated TSS” is actually an estimated TSS that TP calculates. After completing your workout, TP will assign a score in either TSS or hrTSS (and you can toggle between these). Everything in TP is benchmarked against threshold pace or HR. When you see TSS as a score, that score has been given based on your threshold pace/speed, when it’s hrTSS the score has been given based on your threshold HR.
If you have not set anything as your threshold pace or HR yet (or for those on a Base plan who will not be setting these), the numbers you see are pretty meaningless as there isn’t an accurate number set here and therefore it’s an inaccurate representation of how hard your workout was.
On our 3rd call, we will be diving into some of these metrics- what they mean, how they are calculated, how to use/not to use the info, etc.
C.