Different analysts/institutions would use different methods for...

Different analysts/institutions would use different methods for valuing a company. No one can know for certain the value a stock will trade at in the future but it's an educated(calculated) guess based on an assets future supply/demand, technical levels and current fundamental information available.
Price targets can change as new information becomes available, hence why Citi raised their target.
My thought process with high growth potential SSAS like LiveTiles, is that we won't reach that target, but only because this price target is going to keep increasing as new information becomes available.. however as will the share price.