open() built in's doc does not say what the buffering default of -1 means

On this page https://docs.python.org/3.10/library/functions.html#open the signature of the function is shown as:

open(file, mode='r', buffering=- 1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

Notice the spurious space between the - and the 1.

But more importantly, the explanation of bufferings meaning is:

buffering is an optional integer used to set the buffering policy. Pass 0 to switch buffering off (only allowed in binary mode), 1 to select line buffering (only usable in text mode), and an integer > 1 to indicate the size in bytes of a fixed-size chunk buffer.

In other words, it does not explain what the -1 default means. I assume it means "use the default buffering size for the given mode"; but it really ought to say.

从 docs.python.org/3.10/library/functions.html#open 中的 open() 文档页面开始，检查签名和 buffering 参数的说明。完成标准是移除 -1 中多余的空格，并记录 buffering 的默认值意味着什么。