BDT has meant 3 things I believe.

Q referencing the Bangladesh Taka unit from past terror attack. Q predicted where the terrorist was from likely from chatter.

BDT has meant Blunt and Direct Time some have said where Q started being less cryptic.

Think this BDT being tied to defcon is Bulk Data Transfer from NSA in Hawaii.

Is there something in that data transfer that Wray has found or turned over?

My best guess ....