In progress
In progress is the order status that means delivery has started on your order but the supplier has not yet reported the full quantity as delivered.
On an order forwarded through an API, the panel does not watch your profile. It asks its provider for the order status at intervals and copies back what it receives: the status, the start count and a remains figure for how much is still to deliver. If the provider is itself a reseller, it is copying from further up the chain, so what you see can lag behind what is actually happening.
That lag is one reason an order can sit in progress after delivery has stalled. A supplier that has run out of accounts for a service, or has paused it, may leave the order open rather than closing it as partial. Nothing is refunded while the status stays in progress, because refunds are triggered by the status changing. If your count has stopped moving and the remains figure has not changed for far longer than the speed in the service description would explain, ask support to chase it upstream.
Cancelling an order once it is in progress is often not possible, and where it is, the supplier decides. Some panels also show a separate processing status, and what it means varies between panel scripts, so check the panel's own explanation.
What it does not mean
In progress does not mean the order is moving right now. It means the last status the panel received said delivery had begun and was not finished. The remains figure is reported by the supplier, not measured on your profile.