Which side of a shelf liner faces up?
The bumps face up to provide air flow.

This felicitates the complete and continuous drying of tableware which helps prevent the growth of bacteria, especially useful if you like to store your cups upside down.

There is a con to that type you have. Unlike others I've seen that are a sort of nylon web, yours is a solid sheet of plastic. If any water gets under it, it has no way to evaporate. You could put one sheet upside down to protect the cabinet, with another on top for the glassware (or just use one and be sure everything is relatively dry before stowing it).