"*A" is the Star Alliance. When you fly on one airline in this alliance, you can generally credit those miles to another airline's program within the alliance. Each of those programs has a different policy about how many miles they will credit for a certain flight on a certain airline. Those conditions can vary widely and change frequently--there is no standard (althought here are some patterns). For this reason, something like ITA can't tell you how much you will earn, since it doesn't know WHERE you will credit those miles

Put another way: ITA does not have a "cost per mile calculation feature". It has a feature to tell you your total flight miles. Figuring out the accural rate into YOUR preferred program is another step, which you have to do yourself

Example: A Lufthansa flight booked in "W" earns 50% if credited to US Airways, or 100% if credited to United. In another program, it might be 0%. How would ITA know which number to show you?

Partners and booking codes aren't the only time the accured miles won't match what ITA will show. For example, on a "direct flight" (one flight number, with a stop) you may accure miles as if you flew nonstop, even if the stop took you out of your way, because the system might consider that to be "one flight"