Write a Python function to count the number of values associated with a specific key in a dictionary. Return the count.
Example 1:
Input: {"a": [1, 2, 3], "b": [4, 5]}, "a"
Output: 3
Example 2:
Input: {"x": [10, 20, 30, 40], "y": [50, 60]}, "x"
Output: 4