The size in the product name is in centimeters. It is not a clothing size.
Three numbers, such as 24.0x13.0x4.5cm or 20*10*10cm, are the bag's three outer measurements. The x and the asterisk only separate the numbers.
Two numbers are the two measurements given for that bag. One number, such as 35cm, is the single measurement listed.
To think in inches, multiply centimeters by 0.39. A 30cm side is about 12 inches. Use that as a comparison. The centimeter figures in the product name are the listed size.