Why まで in this sentence?


In this sentence (from [here](https://nhkeasier.com/story/2660/))

> このビルは２０階建てで、地下は２階まであります。

the building has 20 floors. Are there 2 basements (perhaps in addition to the
20 floors), or is it that floors up to (まで) the second one are underground
(which there are not in the photograph, it is rather a building on stilts)?




  * n階建て usually refers to the number of floors above the ground (including the first/ground floor).
  * In legal jargon, 階数 refers to the total number of floors including basement floors.

So this sentence usually means the building has 20 floors _above the ground_ ,
plus two basement floors, i.e., there are 22 floors/階数 in total. If you want
to be more specific, you can say 地上20階建て ("20 floors above the ground").

(～まである is a common way to say "to reach ～". It has no exclamatory tone.)

