！！！菜鸟跪求指点-----佣金怎样算？付款方式怎么理解？

我有一个波兰的客户要求我们给佣金，我是第一次接触这个 很多都不懂，请各路大神指点一二，主要内容如下： my commission rates would go as follows: cif poland??1000-10.000usd/eur 3%, 10.001-30.0000usd/eur 2,5%; 30.001 usd/eur and above-??2% from final contract value. if fob china or hk my commission goes up by 0,5% for each final??contract value. shd you accept my commission rates pls, confm 这其中佣金计算的方式 我很不理解。 payment terms applicable: 20% downpayment + balance few days since date of b/l if shpt is made by air, or balance upon??arival notice fm customs agents upon vessel arrival if shpt is made by sea. 这个付款方式 我也不是很一知半解呀，跪求各位大神进来指点一二！！！！