The so-called "consideration" may be explained as the "cost benefit analysis." This is to say, before undertaking any endeavor one must first consider the possible profits and losses. If you find that it's worth the risk--the profit being greater than the loss--then it's advantageous to continue with it.
所謂「算計」，就現代的話說，可以解釋為「成本效益分析」，也就是考慮一件事情，比較它的利害得失，只要划得來﹘﹘效益大於成本，就值得去做。