Exegesis:

kakeinoi (cf. v. 11) ‘and they.’

apelthontes ‘going away,’ ‘going off’: apparently, from the context, the meaning here is that ‘they went back’ to the city of Jerusalem, where the others were. (Of the twenty-one times Mark uses the verb aperchomai, only once – in 7.30 – can it be taken to mean ‘go back,’ ‘return.’)

tois loipois (cf. Mk. 4.19) ‘to the remaining ones,’ ‘to the rest’: that is, the other disciples, ‘those who had been with him’ of v. 10.

oude ekeinois episteusan ‘neither did they believe them.’

pisteuō (cf. Mk. 1.15) ‘believe,’ ‘have faith.’

Translation:

The rest must very often be translated with a more specific referent, ‘the rest of the disciples’ or ‘the rest of those that had been with him.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .