Bonus/scripture issues

This is an additional share given to existing shareholders free of charge.It is normally allotted in proportion of the existing shareholding.so,it is popular to hear of one for one 1:1 or one for two i.e 1:2 or one for four i.e 1:4 etc. A one for one bonus declaration by a company means that for every unit share held previously by a shareholder will attract another unit to itself(free of charge).This means that shareholder who hold 10,000 unit of company "X" at the declaration of 1:1 bonus will now have 20,000 units of that company's shares.Thus,implies that one has a gain of 100% from one's investment excluding capital appreciation and dividend that one may be entitled to at same time.