We have limited the multi-select field to 50 display values to keep the query under control. Every time you open a form with that field in it, the query is transmitted to populate that field with values. You can imagine how this would affect performance if an admin added a couple hundred values.
However, those values are available in the field if you start typing the value. I will use US States and Territories to help explain. For example, if you have "Guam" as a value in spot #52 in the multi-select list types, it will not show, but you can type "Gua" and the search will find it.
Of course this presents a problem with State Abbreviations because the search requires 3 characters in order to work.
So, how many total values do you have in the Custom_States list type? Get that from Admin->List Types->Custom and look at the item count at the top of the Custom_States grid. (If the list type is named something else, sub that instead)
If you have any questions, please contact VersionOne Support.