There we have 4 types of investors in IPO. Categorically they are:
1.Qualified Institutional Buyers(QIB)
2.non-institutional investors (NII)
3.Retail individual investors (RII)
4.High networth individual or investors (HNI)
All above categories of investors have to pass through a specific quota allotment against over subscribe as per SEBI rule to be maintained by the concerned IPO company obviously through computesed method with no chance of manipulation.