Enantiomeric ratios: Why so many notations?

Bibliographic reference: 

Tiritan, M.E., Fernandes, C., Maia, A.S., Pinto, M., Cass, Q.B. (2018). Enantiomeric ratios: Why so many notations? Journal of Chromatography A. 2018. J Chromatogr A. 2018 Sep 28;1569:1-7.