The sorceress decides to activate it in 1000 and to stop it when 500 years has passed on all eras.In the end of time compression people which were in the year 1000 are on the year 1500 obviously.(People who were in 1345 will be in 1845,etc...).
You lost me. Where are you getting it from that TC merely pushes people forward/backwards in time? In fact, compression by definition means the exact opposite. People should be drawn TOWARDS the point where TC was cast, in this case year 1000.

But in fact, there's no way of answering your question because we don't know exactly how fast TC compresses time. We could make an approximation by assuming when Ultimecia activates TC in the game, inside the young Adel, she has been sent back 50 years, making it a total of ca. 70 years away from where Squall and Co are after defeating Adel inside the Lunatic Pandora. Taking into mind that we see effects after like a second, we could approximate the speed as 70 years per second.

Since you're saying that she stops after 500 years has passed in all eras(which would obviously then include her own era from the point where she casts TC), TC must have been working for 500 years at this approximate speed. Let's do some maths, then:

60 seconds in an hour * 60 minutes in an hour = 3600 seconds per. hour.

3600 seconds * 24 hours in a day = 86400 seconds per day.

86400 seconds per day * 356 days a year = 30758400 seconds in a year.

30758400 seconds a year * 500 years = 15379200000 seconds in 500 years.

15379200000 * 70 years per second = 1076544000000 years compressed in 500 years as seen by the one casting it.

So given 500 years with an approximate compression speed, 1076544000000 years would have been compressed in both directions of time, making for a whooping 2153088000000 years compressed all together.

Of course, this mathematical operation is really completely irrelevant, because we don't know really know the first thing about TC, meaning we can't answer your question with any level of certainty. But I suppose to be technical about it, the world wouldn't be on the "brink of time compression" until all of time was compressed except a few thousand years in past and future, which would certainly imply a much wider range than the ones you have given.