query regading promoters contribution in public issue

promoters contribution in public issue as per law

public issue by unlisted company is 20% of the post issue capital

and it also written minimum contribution of rs 25000 per application from each individual and minimum contribution of rs 1 lac from firms and companies shall the eligible to be considered towards promoters contribution

if where promoters minimum contribution exceeds rs 100 crore the promoters shall bring rs 100 crore before opening of the issue and the remaining contibution shall be brought in by the promoter in advance on pro rata basis before the calls are made to the public.

QUERY:

1)what is the meaning of post issue capital?

2)exaplain briefly "minimum contribution of rs 25000 per application from each individual and minimum contribution of rs 1 lac from firms and companies shall the eligible to be considered towards promoters contribution"

3)explain brieflywith example "in advance on pro rata basis before the calls are made to the public."

thanks in advance