Yes, it's a terribly confused explanation of the concept 'equity'. For example it has no way of explaining the difference between the paid-in amount and par value of stock, as far as I can tell (is there a word in English for this difference, btw? In Dutch it's called 'agio' but I can't seem to find one specific word for it in English).
Agio is used in English as well. It is an Italian word denoting the difference of two numbers due to a diverging method of assessing it. It is thus most often used to denote the money banks keep in various transactions. The meaning you specify in Dutch is most closely related to the use of agio to name the difference of the face value of silver coinage and their real metal content.
I think equity is the hardest concept in accounting for people to intuit. It's easy to understand what Assets and Liabilities are, and what Revenues and Expenses are. It's not even that hard to understand accrual concepts of depreciations.
