My story......
Using a 10 Mb download cable speed for my MacMini, it took around 1 hr 15 minutes. Than I got a 20 MBps download modem, and it took less than 35 minutes. One time only, I got what you are describing. Called tech support, had me go through the routine again, then the countdown installer clock showed over 50,000 hours. Had to call tech support again and they did something at there end, ended the call, and tried again, finally the third time worked, but I don't know if that will be the case for you.
Sometimes its the server that is overloaded for the extra delay or something else. Have you tried again by chance ?
I know this does not help, but you might want to call tech support and see if they can assist. They were very helpful, stayed on the line for a good bit of time with me.