I will double check the number of quarts per case on the Mobil 1.
I must admit that makes more sense, but it looked like the size of a case of 12.

The cases of oil I bought in the 60's & 70's were 24 quart cases. The cases of Rotella T, Rotella T Synthetic and the cases of Valvoline and Castrol for my gassers I have been buying for years are all cases of 12. I haven't noticed any cases of 6. Perhaps they are marketed differently in different areas.