TDC updating newbie question

[Zosete]

. It won't update target position. The TVR will calculate lead angles though, which the TDC doesn't do.

Thanks. So it only updates AoB? That's not a big incentive to put the TDC in auto. You might as we'll leave it in manual position. But both the SH3 and GwX faqs and docs insist on turning auto back on once you've entered the data. How does this exactly work?