The word 'erst' means 'only' or 'not until' in the context of time, fitting the sentence 'I come [only] at ten.' 'Dann' means 'then', 'nur' means 'only' (but is more commonly used as 'merely'), and 'schon' means 'already' or 'yet'. 'Erst' specifically conveys the sense of arriving at a later time than expected.