When we say Consideration must be sufficient but need not be adequate. Means that there is no need for each party’s consideration to be equal in value.
Suppose a pen cost $10, and a person pays $6 cash/cheque for this pen, so we know here consideration of $6 cash/cheque is not adequate , in other words, it is INADEQUATE
Now let suppose a pen cost $10, and a person here gives a watch worth $12 in return for buying pen, so here the consideration (watch) is ADEQUATE na?