Apps Update... the old version's still there

[supermum]

Apparently today was "update" day in the app store as half my apps (16!) had updates. However, when it downloaded the updates it left the old ones on my computer. If you look in the "Mobile Applications" folder you will see, for example, Jott in addition to Jott 1.
Since I am sans-iPhone still... my question is, does anyone with an iPhone know what will happen? When the phone syncs does it sync Jott AND Jott 1? Does it overwrite Jott with Jott 1? Should I delete the old versions?
TIA