operator precedence confusion

[Mike McClain]

$ help let says:
The following list of operators is grouped into levels of equal-precedence 
operators.
The levels are listed in order of decreasing precedence.

        id++, id--      variable post-increment, post-decrement
        ++id, --id      variable pre-increment, pre-decrement
        -, +            unary minus, plus
        !, ~            logical and bitwise negation
        **              exponentiation
        *, /, %         multiplication, division, remainder
        .
        .
        .

Hence plus(+) has higher precedence than multiplication(*).
Yet
$ let n=$[1+2*3]; echo $n;
7
or
$  echo $[1+2*3]
7

Shows that multiplication(*) is executed/interpreted before plus(+).

Herein lies my confusion and an explanation would be appreciated.

Thanks,
Mike
--
"Change is not necessary if survival is not mandatory."
    - 'American Bee Journal' Nov. 2019