If it’s dried on and thick you’ll need to carefully dab it with paint stripper using a small tooth or paint brush.
Then very carefully scrape the top surface with a pen knife or Stanley blade, damp the area with cold soapy water to neutralise the paint stripper after.
Then used a car upholstery shampoo on the seat give the painty are a careful scrub, let it dry and then vacuum the seats, repeat if needed.