It means, in 'plain' English...

Look on the sheet called 'another worksheet' in colums A to Q to find
an exact match of the value in cell R243. When found, return the value
in the column number (value in Y2) + 8 that corresponds with this
value*. Multiply the returned vlaue by the contents of cell W243.

*Column A will be column '1', B = '2' etc...