Each pin has a so called subtype associated with it. You have probably noticed that values can only connect with ones of the same type. Like values with values, colors with colors etc. The subtype concept goes into more detail here: It determines whether a value should be edited as an integer or float, determines minimum and maximum values or whether a boolean value should toggle or bang when clicked. A similar logic exists for strings and colors as well. Usually this technique works quite invisibly when editing values, as the user interface magically uses the right metaphors when editing.
The advantage is that e.g. all value pin are compatible, so you can connect value pins of different subtypes at will - internally they are all just numbers, just the editing metaphor changes. Also you can input values which are out of range (as you have done when using floating point numbers to control something which is inherently integer, like a GetSlice). All vvvv´s nodes are designed to deal with out of range values.
The problem is the IOBox. For now the IOBox just takes over the subtype of one of the connected pins (I currently dont know if it is the subtype of the first or the last drawn connection). Kalles module basically connects the IOBox to an input pin which has the subtype set to integer, which in turn switches the IOBox to integer mode. There might be other ways of accomplishing the same.
Bare with us. We know for years that the IOBox needs to be redesigned in a way, that the subtype can be selected or defined by the user. While you can e.g. set the minimum and maximum values, you can unfortunately not set the integer property. But this is a somehow hairy issue with some details which needs to be designed in a right way. Hopefully we´ll find some time soon.