I have a dropdown field with 41 values. These values are a total of 694 characters. When I change the Size value to 700 and save it, it automatically makes the Size 255 and then cuts down the Values field to 255 characters which is only about 1/3 of my Values.
The Selection Limits field has all the correct values in it, ie, it has 41 "0|"s
This should not be an issue... unless you are using a much older version... or your database didn't update with upgrades from the older version you started with.
You can't change the field type to varchar(700). That's not how that works. What you need to do is change...
table: jos_dtregister_fields
field: values
type: text