In P and A modes, the ISO will be raised if the shutter speed goes below the set speed. When your ISO is set to 'auto' in the menu, the criteria for changing ISO will vary according to the mode you're in. The display lies about this, and a high ISO shown on the display will not be used for the shot if it is above the max you set in the menu. If you set a maximum ISO for the auto setting in the menu, you will not be able to select any higher ISO manually. Whenever you select an ISO manually in one of the scenic modes, the setting is carried over to all other modes (including P,S,A and M) if the ISO in question is within your menu-set maximum. Whenever you select an ISO manually in P,S,A and M modes, all the other scenic modes revert to 'auto'.

The display does not show it, since it is calculated on the fly as you shoot. You will not know what ISO setting the camera has chosen for the shot unless you read the EXIF information for the file afterwards.

In this case it simply means that the camera will select a speed equivalent to 1/30, but varied somewhat depending on what lens it senses you have on. Just to add to the confusion, in the shutter speed options there appears another use of the word 'auto'.

However, you should note that the shutter speed of 1/30 is rather conservative if you are using a VR lens, and you might consider lowering it if you have a steady hand. If you manually set ISO at 100, the camera will always start at the lowest possible ISO and boost only by as much as needed. Included in the menu settings are options for choosing a limit to how high the auto ISO goes, and a shutter speed at which the change occurs. If your shutter speed goes too low, the camera will boost the ISO automatically by as many steps as the meter demands. In this option, you set your own starting ISO speed using the dial. Instead, there is a menu setting, whereby you can turn 'auto' ISO on or off. IN P,S,A, and M, there is no 'auto' option among the speeds. If you set 'auto', it will choose its own. If you set a specific ISO, it will use only that. In all other modes EXCEPT P,S,A and M, the ISO choices include all the ISO speeds, plus 'auto' on the dial you use to choose ISO. In Auto mode, you have no ISO input at all. There are actually two entirely different 'auto ISO' arrangements. There is a confusion in the way things are labeled in this camera.

Nikon d3200 settings cheat sheet