First would be how are you "transiting". If you are simply changing aircraft, hanging out in the airport for a few hours, you do not need any visa, you can stay airside, simply showing your boarding pass for the next flight. If your transit involves staying overnight and you want to leave the airport to stay at a hotel, then the transit versus tourist visa headache will show itself.
If you have to leave the airport, I think you will find the visa issue to be one of those "up to the Immigration officer" scenarios. You have a tourist visa, whereas the transit visa is intended for folks without a China visa, allowing them to transit through the country.
You can go to the transit visa counter upon landing and request a transit visa and perhaps the Immigration official will allow it, based on your itinerary. You can't hide the fact that you have a visa, because the transit visa is stamped into your passport as a "Temporary Entry Permit", so the official will flip through your pages and see your visas.
But the official is also allowed to count that entry, as one of your tourist visa allowed entries. From a border crossing point of view, a stay of 24 hours is the same as a stay of 24 days .... 1 entry.