The fraction 51/55 as a percentage is 92.73%. This tells you that the part represented by 51 out of 55 is very close to a whole unit.
Because the percentage is high, the fraction shows that only a small amount (about 7.27%) is missing from a complete set of 55. In everyday terms, if you had 55 items and you already have 51 of them, you’d have almost all of them.
People often use such percentages to quickly see how much of a goal has been reached or how much of a whole is present. Seeing 92.73% lets you understand that you’re just a short step away from 100%.