As others have said, with practice one wants to give the numbers anyway, because this has great benefit in cleansing the conscience and improving one’s life.

… Still, it’s not always easy…
With regard to previous confessions, accept the absolution and direction you have received without revisiting the priest’s judgement. So long as you did not deliberately conceal a mortal sin then the absolution was valid, and, moreover if he has not asked for more information then you should not bring those sins to confession again, unless you recall some information which would have seriously changed that confession. eg. if one had confessed “adultery”, but failed to mention that they had moved in with their lover and been committing adultery frequently and over a long time, then (probably) one should mention that next time.
Priests are very experienced at hearing confessions and know how, and when, to ask questions if necessary. Moreover, in passing absolution they have ruled that your confession is complete with regard to the Church’s requirements.
For the future though, yes, you should mention the number of times a mortal sin was committed, or give a useful approximation, such as “daily”, or “once a month”.
From Canon Law:
Canon 988 – §1. A member of the Christian faithful is obliged to confess in kind and number all serious sins committed after baptism and not yet directly remitted through the keys of the Church nor acknowledged in individual confession, for which one is conscious after diligent examination of conscience.
One is not obliged to confess venial sins, and hence one is not obliged to confess the number of times. For myself, I confess the venial sins which are most troubling me at the time, sometimes with numbers, and sometimes without. eg. “gossiping about members of my own family”, or “spending too much time on the internet, most days of the week”.