Catch some of the fluid in a clean aluminum tray and show it to your tech if you don't recognize it. ATF leaks are common after sitting for a few days as the torque converter drains back into the transmission and the fluid level rises in the transmission pan. If it only leaks after a few days and it is ATF and it is slightly to the right side of the car off-center, look at the two piston covers just above the pan gasket.

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