Hi @esebelius
the answer is it depends. If it is an MLB event you enter the barcodes and the tickets will be removed from your account. If mobile transfer you will be given the buyers name and email and you will be responsible for making the transfer. Remember after transfering to confirm you have done so in your stubhub account.
Typically with Ticketmaster or AXS tickets you would transfer 2 tickets from your Ticketmaster or AXS account to the buyer. It sounds like your tickets are not Ticketmaster or AXS? I don't know where your tickets are living, but with Stubhub you need to transfer the tickets you sold to the buyer. Providing the buyer with a link will not be acceptable, and as you said if you did that then the buyer has access to all 4 of your tickets.
I suggest removing your listing before it sells until you have an understanding on if you can transfer tickets from whatever web site they are currently living in because if the tix sell and you can't properly transfer them to the buyer you will get a 100% penalty for not being able to fulfill the sale.