Yes, it does affect your account balance. On debit card purchases, merchants may request temporary holds on accounts. This hold is placed by the merchant, and Novo is not responsible for debit card holds. This is common, and will eventually be adjusted to the actual amount of your purchase.
Please note that the length of the hold is dictated by the merchant at the time of authorization, and only the merchant has the power to lift that hold in advance of the originally specified timeframe.
It is common for merchants to initiate 30-day holds during the original authorization. To avoid an accidental overdraft, the funds available in your account may be reduced by the amount of the temporary hold. If your hold exceeds your account balance, your account can be in overdraft.