Under New Built-in Functions :: Position:
(...) In the second form, an offset position may be
supplied so that the function returns a result relative
to that position in the outer string.
This is incorrect. The result is always given relative to the start of the string.
Providing an offset position only causes any earlier matches to be ignored.
position ('be', 'To be or not to be', 10)
returns 17, not 7.