The proportions of public issues of shared allocated to various category of investor is
In IPO allotment is based on regulatory guidelines. The information allotment is categorised by the number of shares applied by investors.

In case of a public offering, there are different types of investors such as retail investors, Qualified institutional buyers (QIBs). High net worth individuals (HNis)
In case of QIBs, shares are distributed proportionately to the applicants. For instance; if the shares are oversubscribed by 4 times, then an application of 10,00,000 shares will receive only 2,50,000 shares.
In the case of retail investors, they can apply only with the provided range of 10-15k to 2 lakhs.
Eg. If the retail investor buys a share at a bid of Rs 270. The sum of his total application would be Rs 270 * 50 = Rs 13,500.
in case if HNIs, these individuals invest in huge amount in IPO. The allotment of shares in HNis is adjusted according to the number of the subscription. If the shares are oversubscribed HNIs may receive lesser shares then applied.
For instance; If an HNI has applied for 10 lakh shares. It is now over-subscribed by 150 times. The total shares that will be allotted to him will be 6666.