Or you could say Studying Apr 2013, Working Apr 2013 because you graduated on Apr 5th and started working on Apr 25. That’s perfectly fine as well .
However, if you said Studying Apr 2013 and working July 2013, you would have to account for the months in between. You might say “Unemployed: May 2013 – Jun 2013” and that would be fine.
IRCC doesn’t want to see any large gaps or unaccounted time in your history.