You must use the terrain table for attrition. I do not know why the rules say unit type, but I suppose it is my fault. The OOS unit consults the Attrition column on the TET and rolls 1d6. If the result is less than or equal to the number indicated, the unit receives 1 Combat Hit (CH). Units that are completely surrounded by enemy units or enemy ZoC roll 2d6 for attrition and can receive up to 2 CH.