If...then vs If (Had vs. Were)

The sentence here is a 'IF.....THEN' tense construction. Not a 'IF...' subjunctive construction.

Here, the sentence reads something like..
'If you had won the lottery, you would have given half the money to charity'.

In a subjunctive 'If' construction, the examples can be '
If I WERE rich, I would donate money to rebuild my old school'.