Yes, that is correct. getIndex() is 0-based and getCount() is 1-based.
Following is an extract from the JSTL 1.1 specifications document ------------------------------------------------------------------
public int getIndex()Retrieves the index of the current round of the iteration. If the iteration is being performed over a subset of an underlying array, java.lang.Collection, or other type, the index returned is absolute with respect to the underlying collection.
Indices are 0-based. Returns The 0-based index of the current round of the iteration
public int getCount()
Retrieves the count of the current round of the iteration. The count is a relative, 1-based sequence number identifying the current round of iteration (in context with all rounds the current iteration will perform). As an example, an iteration with begin = 5, end = 15, and step = 5 produces the counts 1, 2, and 3 in that order.
[b]Returns/[b] The 1-based count of the current round of the iteration