!!! Overview
[{$pagename}] is a [Certificate] [Basic Constraint] defined in [RFC 5280] a field is meaningful only if the [CA Constraint] [boolean] is asserted and the [KeyUsage] extension, if present, asserts the [keyCertSign] [bit].  

In this case, it gives the maximum number of non-self-issued [Intermediate Certificate] that may follow this [certificate] in a [valid certification path|Certificate Chain].  
(Note: The last certificate in the certification path is not an intermediate certificate, and is not included in this limit.  Usually, the last certificate is an end entity certificate, but it can be a CA certificate.)  

[{$pagename}] of zero indicates that no [non-Self-signed|Self-signed Certificate] [Intermediate Certificates] [Root Certificate] may follow in a valid [certification path|Certificate Chain].  Where it appears, the [{$pagename}] field  [MUST] be greater than or equal to zero.  

When [{$pagename}] does __NOT__ appear, no limit is imposed.

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