supplementary plate meaning in English

辅助字牌；辅助指示牌；辅助标志牌

A warning sign with supplementary plate
附有辅助字牌的警告标志
Image : 84i . gif a supplementary plate used with parking signs showing the maximum charging period
Image : 84i . gif附于泊车处标志下的时间牌
Supplementary plates may give additional information or exemptions to the ban
禁制性标志之下的辅助标志牌，说明附加的指示，或豁免管制的规定。
Advanced warning of restricted headroom may be given by a restricted headroom ahead warning sign with a supplementary plate showing the distance to the restriction
前面有通行高度限制的警告标志，用以预先警告驾驶人，并有辅助标志牌，说明限制生效的地点距离有多远。