Both are technically correct.
a) The stock market is where it is at at Christmas
b) The FTSE 250 stock market has suffered a fall of 2300 from 17300 to 15000
Both correct. But the context is all important. Since Christmas, it was growing.
TBF - it's up again but these are volatile times. Saying it's back to Christmas levels lack context and are a bit misleading spin.