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

Calling ranges are tighter

Pre-flop
Blinds 400 / 800 (100 ante)Pot 11,100 (13.9 BB)Your M = 4 • Red zoneBBK♠10♠● 8,400 (10.5 BB)YOUto actMP● 9,000 (11.2 BB)Short stackall-in 9,000 (11.2 BB)SBfoldsD

Red zone (M 4). An early-position short stack open-jams about 11 BB, and you hold K♠T♠ in the big blind.

An early-position short stack jams; you hold K♠T♠ in the BB. Best?

WhyFold. You'd happily open-jam K-T suited first-in, but calling a shove is different: you need a hand that fares well against his early-position jamming range and you get no fold equity. K-T suited is dominated too often here - fold.
What happensYou fold.  Your call-off range is tighter than your push range.
Pushing and calling are not the same: when you shove you have fold equity, but when you call you only have your equity against his range. So your calling range is significantly tighter than your shoving range.

Call shoves with a tighter range than you'd push - calling has no fold equity, so you need a hand that beats the jamming range.