If you are the Sender then I would suggest just to go into "Correct" on the envelope, check the values and then exit correct mode (Discard Changes). Therefore you see the settings chosen without making any changes to the envelope.

When envelopes are created they use the default set for the Account. So if the default is set under Admin Console > Reminders and Expirations, every new envelope should use these values by default whether creating one envelope or 300 using bulk send.

Unfortunately if you sent out 300 envelopes and the Reminders were set to 3 days, there is no way to my knowledge to bulk change all 300 envelopes to say 5 days instead. You would need to correct each envelope.