Using an iPad Air 4 with the most up to date IOS it will generally give me an estimated time of 25 minutes but this rapidly changes and the actual time taken is between 11 and 15 minutes. When loading from the phone (iPhone SE2) the estimated time is 25 minutes but the actual time is 13-18 minutes.
On the phone there are 3 locos in the engine shed on the iPad there are about 20, with a mix of tsx, tts and non Hornby sound decoders, non Hornby silent DDC decoders.