ISO 3613-2010中有错误？

能否将你计算过程简单说下呢？

1 ml of this standard solution contains 0,1 µg of Cr(VI).
For the preparation of comparison solution, add 1 ml of phosphoric acid and 1 ml of diphenylcarbazide
solution to 50 ml of standard Cr(VI) solution,
标液中六价铬含量为0.1ug/ml
取50ml显色
Cut a test piece measuring about 50 mm × 50 mm from the coated item and remove any sealing, such as
paint or wax, etc., by scraping the surface.
取试样25cm2，萃取，定容50ml，显色
与标液比较
那么，0.1ug/ml*50ml对应25cm2
不就是0.2ug/cm2

单位不是毫克每千克 with五十平方厘米吗？是不是写错了？

楼上样品的面积算错了
面积应该是25*2=50