How did you dream of picking lead from crabs?

Dream of picking up crabs by lead, about the duke of Zhou has the following statement:

Pregnant women dream of picking crabs and getting lead, which indicates that the baby can be born healthily and there will be noble people to help in the future. Candidates dream of picking crabs and getting lead: it shows that your recent exam results are not good because you are usually playful. I hope your grades will improve in the next exam.