"which essentially means that Samsung demands a 100% tax abatement from the county and 50% from the city."
So the figure couldn't really be much larger.
50% tax abatement for 5 years from the City (which has a ~50% higher tax rate than the county). I can think of a lot of ways it could be much larger. How about 100% abatement for 5 years? 50% abatement for 20 years? 100% abatement for 100 years?
"50% abatement for 20 years?"
The article reads like that's what they are asking for from the City.
They are asking for 50% for 5 years for the city (which has a higher tax rate), and 100% for 20 years for the county (which is a smaller govt entity with a lower tax rate).