ad (preposition?)

[Gavril]

From a description of a cardiac medical study:

Nykyään toimenpidevolyymi on keskimäärin 150 läppäasennusta vuosittain ja maksimissaan niitä on tehty ad 180/vuosi.

"Currently, the volume [of procedures performed in the aforesaid region] is 150 valve implantations per year on average. At maximum, [???] 180/year of them have been performed."

The highlighted word "ad" seems to be a Latin preposition (meaning "to"/"towards", among other things). But how is it functioning in this context?

Thanks for your time

 

[Maunulan Pappa]

"Up to."

"Ad" is used, I guess, because the Finnish "180:een saakka / vuosi" would be rather cumbersome.

Edit: Yes, "ad" comes from Latin, and as far as I know, it is widely used in this manner in the medical context but not much elsewhere.