It is important for you to understand that the cards and reply page you design are online.
When your recipients click on the envelope e.g. in the email they received, the browser opens and the envelope animation starts or the card is displayed.
The card(s) that are displayed in the browser are always the latest version.
So, if you designed your card and sent it to e.g. 10 recipients.
Then, you noticed a spelling error on the card and corrected it.
If you corrected it before a recipient clicked on the envelope in the email, no recipient would have seen the error.
This is also important when you are sending e.g. Thank you cards to individual recipients.
If you wish to edit personal text for each recipient, you need to copy your first event into new events for every recipient.
Please do not send the card from the recipient list and then go back to the DESIGN tab, change the text for a 2nd recipient and then go back to the RECIPIENTS list and send to this 2nd recipient.
If the 1st recipient opens his sending after you edited "his" text on the card, he will see the card text you wrote for the 2nd recipient etc.