D0.50ct means that the diamond size is 50 cents, d5.00ct means that the diamond size is 5 carats, and d0.05ct means that the diamond size is 5 cents. The weight of diamonds is in carats, and the weight of diamonds less than 1 carat is expressed in minutes (pt). There is a conversion formula between ct and pt: 1 carat (CT) = 0.2g = 100 minutes (pt).
size
Ring refers to the standard of circle size, called hand inch, calculated by numbers. Hand-inch is divided into Hong Kong style and American style, and China mostly adopts Hong Kong style. Most people's hands are between 4 and 26 inches. The safest way to measure is to ask the clerk in the jewelry store to measure for both of you, or you can measure yourself by the method published on the Internet: find a rope or a piece of paper, wrap it around the place where your finger will wear a ring, mark the overlapping place on the rope or paper with a pen, then measure its length with a ruler and compare it with the hand-inch comparison table.