Hello A K
Once the order is placed, your seller has up to 24 hours to decide whether to accept or reject it. If you placed the same-day order, the seller would react faster. And a seller has 100 hours to deliver all visitors to you from the date on the order page.
I'd suggest visiting our Help section. There is a detailed tutorial on how does Udimi works.
Contact our Live Chat support from the Help section if you'll have any further inquiries.