It's a bit more complicated than that. On a plan with Smart Browsing when you use up all your data you will still be able to do basic browsing without too much difference, essentially unlimited browsing.
However, everything you do online consumes data and counts against your data allowance, including browsing. Your plan has a set amount of gigabytes for Anytime and Bonus time use that will be used whenever you are on the internet.
Can explain further if needed.