I think I might be confused about calorie limits?

I am new here to the site and to calorie counting.  I think that I am reading different info but am not sure.  I weighed in last week on sunday at 314 and would like to get down to around 140 or so.  When I go to the burn meter it says that I burn 2500 calories just existing.  I am trying to ride the bike for 25 minutes 2x a day to burn another 500 or so.   I am trying to keep my calories to just under 1500 and am doing pretty good at it.  What Im confused about is, I keep reading that the difference between the calories that I eat and burn shouldn't be more than 1000.  Why?  Will it hurt?  I can't imagine going into starvation mode.  I did Medifast for 6 months and only consumed 550 calories a day (really dumb now I know).  But I really have lots to lose and need a good first few months to get me going at least.   I cant wait to weigh in tomorrow.  Maybe I have just read stuff wrong and it is me that is confused.  Definately would not be the first time.  Thank you for the help.

I would say that a 1000 cal deficit is more than enough - you don't want to pack on the pounds once you're done. Losing it slow and steady is INFINITELY better than shedding them quick to only put them back on because your body thinks you're starving!

Good luck, and message me if you need anything!