If you've got a date and time that would work for different clients, you don't need to wait to hear back before offering it to the next person. Send that same date and time to as many clients as you like, all at once. As soon as one of them books it, it automatically becomes unavailable to everyone else you sent it to. There's nothing more for you to do and no risk of that date and time getting booked twice.
This is what keeps you protected from double bookings. Rather than trying to remember who you've offered a date and time to, Get Ink handles it for you. The moment an appointment is confirmed the other clients will see the date and time marked as unavailable on their personal link. You never end up promising the same time to two people by accident.
It's a quick way to fill your diary without the back and forth checking availability with each one first. You don't have to worry about double booking anybody.