Part: Part Nine - Inflection Points: M, Q & the Zones

Calling a late jam

Pre-flop
Blinds 400 / 800 (100 ante)Pot 12,100 (15.1 BB)Your M = 6 • Orange zoneBBA♣9♣● 12,600 (15.8 BB)YOUto actBTN● 10,000 (12.5 BB)Short buttonall-in 10,000 (12.5 BB)SBfoldsD

A button short stack open-jams about 12 BB, the small blind folds, and you cover, holding A♣9♣ in the big blind.

A button open-jams ~12 BB; you hold A♣9♣ in the BB and cover. Best?

WhyCall. A button open-jamming ~12 BB has a wide range; A-9 suited is ahead of it and you're getting a good price closing the action. Calling ranges versus late-position jams are far wider than versus early-position ones.
What happensYou call and are in good shape.  Late jams get called wide.
Position cuts both ways: just as you jam wider from late position, you must call jams wider when they come from late position, because the jamming range is so wide.

Call late-position jams with a wide range - their shoving ranges are wide, so your calling range expands accordingly.