Days not hours

I am trying to recover from a Seagate HDD. I started the process on my old laptop which is a Windows 7 2,40ghz Duo CPU running 4GB of ram it quoted the recovery time as 4 days. I then moved the drive to my desktop which is Windows 10 AMD 8 core 9590 running with 32GB DDR and twin GPU's, I am now being told its 14 days! Any clues or ideas why this may be the case please.

At a guess this is because "time" means Estimated time. at some point as it scans the time estimated will suddenly drop to a more manageable 4 days.

At another guess (completely unrelated from the one above), second computer has more occuring in background and can't give Recuva as much juice as the first one does.

Many thanks for taking the time to repond, the "time" moved overnight to 24 days estimated time and 1% completion. The second computer has no background programs running and is about as fast (AMD wise) as you could get last year. I've looked at all the obvious things and I've used Recuva before and think its a fantastic program so I'm a bit perplexed really.