Exemptions

Head of Household includes the taxpayer and one exemption.  In my case I have 3 dependents (two college students and one high schooler - I provide their support).  Why, when I file my federal 1040 am I only given $18,800 exemption when I have 3 dependents, not just one?  Should not the $18,800 be increased for my two other dependents, especially when they worked part time last summer and when they filed their 1040s, they noted that they were "claimed as dependents on another tax filing (mine)?  Also, they owed taxes and had to pay on the state.  Is $18,800 the cap on the exemption so whether I have 1 dependent or 6, it will not matter - that $18,800 is the maximum exemption no matter how many dependents I have?