Start time
Start time is how long an order waits between being placed and delivery actually beginning, usually shown in the service description as an expected range.
The wait is made of several queues. The panel forwards the order through its API, sometimes through more than one reseller, and each hop can add its own delay before the supplier that delivers it picks it up. The supplier then works through orders placed before yours. A start time written into a description reflects what that service did when the description was written, not the queue at the moment you order.
While the order waits, the link has to stay exactly as it was. Switching the profile to private, changing the username or deleting the post before delivery starts can get the order cancelled or leave it delivering to nothing. And because the start count is recorded when delivery begins, any drop on the account during the wait is invisible to later refill checks.
The costly mistake is treating a late start as a lost order. A second order on the same link at another panel can mean both deliver and both are charged. Some panels reject a new order on a link that already has an active order, so the duplicate tends to happen across panels. Ask support about a slow start before ordering again.
What it does not mean
Start time is not delivery time. An order that starts quickly can still take days to finish at the stated speed, and a stated start time is an estimate, not a commitment.