Is a presumptuous sin considered a double sin?

Knowingly doing something you shouldn’t and assuming that you will be covered by mercy could lead to double trouble.

“But the person who does anything presumptuously, whether he is native-born or a stranger, that one brings reproach on the Lord, and he shall be cut off from among his people. Because he has despised the word of the Lord, and has broken His commandment, that person shall be completely cut off; his guilt shall be upon him.”‭‭Numbers‬ ‭15‬:‭30‬-‭31‬ ‭NKJV‬‬

Confess your sin, and you will be forgiven, “If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.” 1 John 1:9