Each Round Robin sample set contains the velocities range notes. So, in this case, the crash1_bow contains two round robin sets (R1 & R2) with four (4) velocities each, totalizing up to eight (8) different sounds.
This creates more flexibility to quickly create different versions of a sound*.
The outcome produced (see left picture) shows the R1 or R2 identifier on each sample name added when Round Robin option is selected. Note that crash1_bow_18_R2_004.wav and crash1_bow_18_R1_004.wav are two different sound samples generated from the same MIDI note at the same velocity and so on.
(*) Source has to be able to generate a different sound for each triggered note, otherwise, sound will remain the same. Please check that your VST/AU/Hardware Synth/Module is able to generate different sounds on same velocity note.
For additional information, please also check the Questions and Answers page here.