Lua string.find语句问题

Question

s,e=string.find("hello Lua users","Lua")
print(s,e)

结果为7 9

在manual里看，也没有看懂。为什么会是7,9？
* 附：

string.find (s, pattern [, init [, plain]])

Looks for the first match of pattern in the string s. If it finds a match, then > find returns the indices of s where this occurrence starts and ends; otherwise, it returns nil. A third, optional numerical argument init specifies where to start the search; its default value is 1 and can be negative. A value of true as a fourth, optional argument plain turns off the pattern matching facilities, so the function does a plain "find substring" operation, with no characters in pattern being considered magic. Note that if plain is given, then init must be given as well.

If the pattern has captures, then in a successful match the captured values are also returned, after the two indices.

Answer 1

突然发现自己蠢了一下，已知道答案。