There isn't any limit on the number of links you can include on your Link-in-bio page, but your account does have a monthly limit on the total number of links you can create in Bitly. This limit applies to (and includes) any links you create specifically for your Link-in-bio page.
You can also use any of the links you've already shortened in your Bitly account on your Link-in-bio page, without any limitation.
Your monthly limits reset at the start of each month.