Did you run the engine for a couple of minutes after adding the new oil?
Normally one should drain the oil, change the filter, add new oil (up to full mark. This may be a bit less than 3.2 quarts), run the engine for a couple of minutes, top up. Topping up is best done after letting the car sit for a couple of hours, so that most of the oil has the chance to flow down to the pan. Doing so you will probably notice that the level is a bit less than full, since some of the oil stays in the filter. Topping up should probably bring it to 3.2 quarts mark.
Another thing could be that the car was leaning a bit towards the rear when the oil was drained, thus leaving a bit in the pan. One can jack up the rear of the car to drain the oil more completely.
But this is doing a "laboratory precision" oil change and is a bit overkill
The amount of added oil being 2.5 quarts, I would think it was not drained completely. The filter cannot hold more than, say 0.1 quart.
There is no need to redo the oil change though. Make sure that the level is where it should be and call it a day.
Some say to warm up the engine before draining the oil, thus making the oil flow better and easier to drain completely. Critics claim though that quite a bit will likely remain in the passages not having enough time to flow down.
Others say to let the car sit and wait for all the oil to flow down to the pan, then drain it. Critics say, that the potential contaminants in the oil will no longer be suspended in the oil by the time the oil is drained, but will be left at the bottom of the pan. Thus contaminating the new oil.
Personally I'd say that as long as your engine is clean to begin with and well-maintained, it does not matter. Do whichever way you like.
If the engine on the other hand is filthy and poorly-maintained, choosing one method over the other is not going to clean or contaminate the pan in a noticeable way anyhow.
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