Don’t have answers for the math differences, but I think it’s best to look at this from a higher level.
The advice is as of this moment based on your current settings and historical activities.
Your IR (improvement rate) setting controls the XSS and hours/week guidance along with intensity…
What is ramp rate set to currently?
As a test dial IR down a level and note the immediate changes to XATA and the pacer needle.
XATA is based on a rolling seven day period and recognizes weekly patterns. If you rode long last Tuesday that’s noted in recommendations for this Tuesday. However, that’s not to say you must do the same thing this week.
XATA is advice and general guidance, not a prescription down to the minute or day. You are free to change your schedule and ride volume and allocate your days over the week as you see fit. You could ride longer to compensate for a deficit or create a surplus by exceeding a daily target. But there is no need to wipe out a deficit or worry about a surplus. The numbers even out over the rolling seven days.
Your main goal is to keep the pacer needle pointing up between 11am and 1pm if you want to achieve the TL ramp rate you established by your IR setting. If TL becomes too much to handle, lower IR for a week or take extra rest days and ignore any deficit created. It will be gone next week if you are back “on schedule”.
Think of XATA’s numbers as guidelines for a range of possibilities. You decide what to do within those guidelines. Your legs (and schedule) will tell you if you have taken on too much or can handle even more.
Reference:
Beginner’s Guide: Improvement Rate – Xert (baronbiosys.com)
Improvement Rate – Xert (baronbiosys.com)
Training with the Xert Adaptive Training Advisor – Xert (baronbiosys.com)
If you are new to Xert lots of tips are posted in this thread –
Beginner questions - Support - Xert Community Forum (xertonline.com)