This shouldn't be a problem. We don't do font changes. We have a character limit on the create page to make sure there are no major errors when designing the star map on mobile or desktop.
If for example you need the text to be sentence style or in italics, or a longer title, emoji's, or a foreign language, or if you prefer the text to be bigger or smaller, then we can manually edit the print for you. In this case as soon as you have placed your order send us an email to email@example.com with your order number and edit request and we will do our best to fulfil it for you This can take our design team up to 24 hours to complete. Again you need to send the email within 24 hours from ordering if using standard or free shipping and within 4 hours if using express shipping so that there is still time to make the changes you want. We will send you a preview if you request that, so that you have a chance to approve the changes before we return to the print queue.
Hope this helps!