Hi,
So there are (confusingly) three features that make suggestions:
password manager - this understands that you have usernames and passwords associated to a given site
credit card & address autofill - this understands names, mailing and email addresses, and payment info
autocomplete - this just remembers text you've previously entered into a given field, without any understanding of the text
When Chrome both recognizes the form and has data of the appropriate type to offer, you get suggestions from either password manager or autofill, depending on the the type of form. Otherwise, Chrome falls back to suggesting something it has seen you enter into the form before (i.e., autocomplete).
Unfortunately, there's no real UI for the autocomplete data; but, if you have sync enabled, you *can* see your autocomplete data in chrome://sync-internals in the "Sync Node Browser" tab under the "Autofill" folder. The data is just a collection of {field name, value} pairs. You can cause this data to be deleted using "Clear browsing data" -> Advanced -> "Autofill Form Data". The UI will inform you of how many credit card, addresses and "others" will be deleted. The "others" are the autocomplete entries.