The V-150 Commando in its 20mm version carries 6+6 rounds HE/AP in the OOBs where I found it - for example with Trukey: Unit 52; Thailand: Unit 100; now,
http://www.globalsecurity.org/milita...150-specs.htm; Tanks of the world, ed. 8; and other sources all say it has 200 rounds ready + 200 reserve, 400 in total - this should then be 20/20 in the game I guess.
Besides, in the OOB of Saudi Arabia I found a version - Unit 123 - with the only armament being a 20mm cannon and only 12x HE ammo - that might be a mistake.