Regent Trouser Sizing: The number you see refers to waist size, whilst the letters S, R and L refer to leg length. S is Short (length 30), R is Regular (length 32) and L is Long (length 34).
The drop crotch on these means they're designed to be worn lower about the hips, rather than sitting up on them.
Feel free to message Jason via the Whatsapp Chat button on the bottom right of your screen, and he can send more pictures of the product and answer any questions you might have about size, styling, fit, colour, etc