CFA一级 Interest Rate Risk的疑问 before, return, period, purchase, investor

judo

请教一个问题：
If the market YTM for the bond, our assumed reinvestment rate, increases after the bond is purchased but before the first coupon date, a bond investor will earn a rate of return that is lower (higher) than the YTM at bond purchase if the bond is held for a short period.                                    

If the market YTM for the bond, our assumed reinvestment rate, decreases after the bond is purchased but before the first coupon date, a bond investor will earn a rate of return that is lower (higher) than the YTM at bond purchase if the bond is held for a long period.         这两段话是什么意思？ 这两段话中都有lower (higher) ，这是什么意思？ 谢谢！