Discount Voucher

last month, I wanted to buy a gamepad for my laptop. So, I was looking for a good and trusted online shop. Finally, I found the website and I got a 30% discount voucher for all items. Then, I found a gamepad I was looking for. It costs around Rp. 400.000, it could have be a good gamepad for its price . I know it was pretty expensive for a gamepad, but then i remembered that I have a discount voucher, so it could have been cheaper. So, I was thinking to buy it and I proceed to the next step of payment.
When I was going to choose the payment methods, I used the discount voucher. But when I used it, the price only go down by Rp.30.000 not 30% of the price. I was confused about it and I tried to read the Terms and Conditions about the discount voucher. Then, I read that the maximum of the discount is only Rp.30.000. I was really disappointed so I canceled it. I should have read it carefully.