salaam i have mixed and spend the amount on which i had paid khums today, should i deduct the amount on which i had paid already and pay on the balance?

Walaikumussalam
May Allah accept your aamal and ibadaat and give barakah in your rizq
Aameen
Yes you deduct the paid one and pay khums on your additional saving which is consider as saving of the year
Wassalam
Syed Abul Qasim Rizvi