Hi,
I'm afraid that your question is more related to HikaShop than HikaSerial.
The HikaSerial coupon generator will create a coupon using your "coupon template", for the rest it is still an HikaShop coupon.
And I think that you will have the same issue with a coupon created manually with the same configuration than your coupon template (or directly your coupon template, if you published it).
The best would be to create a new thread in the HikaShop forum section with a screenshot of one of your coupon and the same explanation of the issue you wrote here.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.