Hi,
Sure you can.
Because the "span" which set the fond-size to 12px has been added by "yourself" in the product description ; I think that your WYSIWYG editor should have add it, but it's not related to any code in HikaShop. You just need to modify the product description content.
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.