Let us examine the two theories of value, by way of example:

Let us say that you wish to have a desk constructed.  The plans have been drawn, the specifications precisely set down as to size, material, finish, etc.

You approach an individual who has the reputation of being a good cabinetmaker, and ask if he will construct the desk to your requirements.  He agrees, and quotes a price of $400 for the finished product, to include the costs of acquiring the materials, and for his time and effort in constructing the desk.

When the desk is completed, you pay the man the agreed-upon price of $400, and take possession (ownership) of the desk.

At  this point, Smith and the other labor-value economists have been fully satisfied.  The labor involved in the desk has been paid in full.  The cost of the desk was $400, the price was $400, and the desk's objective value has been set at $400.

Now, let's take the example one step further.

Say you keep the desk for  short time, and then decide you no longer want it.  Someone offers to buy it, and you sell it to him for $500.

Now you are frowned upon by the labor value theorists.  You have unfairly profited by $100, simply by re-selling a desk that cost you $400.

Remember, according the the labor theory, the desk has an "objective" value of $400 as a result of the labor expended.  The $100 is in excess of that amount and is thus deemed to be a "surplus value".