When Sn reacts with calculated amount of HgCl2 and excess HgCl2, then the product will be respectively.
This is one of the cases in chemistry where you will see that the amount of reactant is very important to get the product.
When Sn is heated with calculated amount of HgCl2, anhydrous SnCl2 is formed.
Sn+HgCl2→SnCl2+Hg
and, by heating Sn with excess of HgCl2, Stannic Chloride is formed.
Sn+2HgCl2→SnCl4+2Hg