Welcome to the community @reginab!
The definition of the numbers will show on the bottom of the page under: " See Full Details "
For example 5 is:
Additional data in $5 or $10 increments (as indicated). Data overage protection feature will prevent overage fees over $50, unless you choose to continue incurring charges. Roaming charges apply when not on the Fido network or in an Extended Coverage area within Canada; fido.ca/roaming.
The list is too long to put here but you can view it yourself once you go on Fido.ca. Hope this helps.