4 1/2 or 5 quarts of oil with 1/2 quart of ZZDP?

DartGTDan said
I will be changing the oil & filter in my 318 shortly. My engine builder told me to include a 16 ounce bottle of a ZZDP oil additive with the fresh oil and new filter.

My question is do I use 5 quarts of oil + 1/2 quart of ZZDP additive?

Or, 4 1/2 quarts of oil & 1/2 quart of ZZDP equaling 5 total quarts?
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May be just my OCD issues but I would mix the oil and additive together with a drill and paint paddle prior to adding it to the engine. Not claiming this is the only way. Just my two cents./