Answer: The Cinderella bush-type pumpkins take an average of 95 days so they are a bit earlier than say the giant pumpkins would be. However, it sounds like your pumpkins were developing right on schedule. It can take many weeks for them to completely ripen and they taste best and keep longest if allowed to remain on the vine until fully mature. This is especially important with the Cinderellas because they are not particularly "good keepers".
If possible, it's best to plant pumpkins late in the spring and then wait until a frost kills the vines, which signals the pumpkins to ripen and develop a hard shell. (A light frost actually improves the flavor of pumpkins by changing some of their starch into sugar.) A quick field-test to see if your pumpkins are mature is to try to press your fingernail into the skin of the fruit. If you can break the skin, the pumpkin is immature. If the skin is hard, the pumpkin is mature.
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