Hello aspirant,
As per your query you need to know that during percentage calculation, It is calculated using best of 5. But, A language subject such as English in your case is necessary. It can't be replaced So, basically its- 1 language subject + 4 other best scored subjects of yours taken into consideration in percentage calculation.
So yes, your additional subject will be taken into consideration.
But try your best to score more .Good luck!
Hope it helps,thank you.