Returns the number of transfers the Source is ready to supply, upon demand. This is a runtime, read-only property.
|ActiveX Edition||Plug-in Edition||Mac Edition|
|Since V1.0||Since V1.0||Since V6.4|
This property is valid only in OnPostTransfer event.
The Data Source returns -1 if it is not sure how many transfers are pending. Scanners with ADF (Automatic Document Feeder) will typically return -1 if the current image is not the last one.