这是什么意思，实在不懂

老外发给我一句Pls be little more serious ok，直译我明白，可是我觉得 serious 不是严重的意思诶，各位能否帮忙想想看是啥意思 他这句话是回我这封邮件对的： I understand your suffer, and I believe that you will pay the sample charge finally. However, we also need your trust. After the order placed, you could deduct this cost when balancing the payment. I promise that you will like our product for its high quality.What's more, we he our own factory. You could transfer the money into our company account and kindly send you address to me . I hope we could come to an agreement at last. Looking forward to your reply. Sincerely, Linda