The xsl:number element first constructs a list of positive integers using the level, count and from attributes: When level="single", it goes up to the nearest ancestor (including the current node as its own ancestor) that matches the count pattern, and constructs a list of length one containing one plus the number of preceding siblings of that ancestor that match the count pattern. If there is no such ancestor, it constructs an empty list. If the from attribute is specified, then the only ancestors that are searched are those that are descendants of the nearest ancestor that matches the from pattern. Preceding siblings has the same meaning here as with the preceding-sibling axis; thus neither attribute nor namespaces nodes have any preceding siblings. When level="multiple", it constructs a list of all ancestors of the current node in document order followed by the element itself; it then selects from the list those nodes that match the count pattern; it then maps each node in the list to one plus the number of preceding siblings of that node that match the count pattern. If the from attribute is specified, then the only ancestors that are searched are those that are descendants of the nearest ancestor that matches the from pattern. Preceding siblings has the same meaning here as with the preceding-sibling axis; thus neither attribute nor namespaces nodes have any preceding siblings. When level="any", it constructs a list of length one containing the number of nodes that match the count pattern and belong to the set containing the current node and all nodes at any level of the document that are before the current node in document order, excluding any namespace and attribute nodes (in other words the union of the members of the preceding and ancestor-or-self axes). If the from attribute is specified, then only nodes after the first node before the current node that match the from pattern are considered.