Are the notes/values being added by the user(s) or through workflow? Based on the screenshot it looks like you're doing it with Workflow in which case you can "prepend" the values fairly easily.

All you need to do is the following:

1. Retrieve the current value(s) from your multivalue field
2. Select "Replace" instead of "Append" when setting the field value
3. Add the new value in line 1, and the token for the current values in line 2

So, if you start with a value of 1, then add a new value of 2, it will insert the 2 followed by the existing value of 1. If you then add a 3, it will insert the 3 followed by the existing values of 2 and 1, and so on.

Each time you add a value, it will go to the top and all the previous values will be moved to the bottom without having to build any complex sorting mechanisms.