Spec doesn't state whether fifth and successive chars in delimited block markers must match fourth char

[scouten]

In Summary of structural containers, the spec shows the initial (typically four) characters of the delimited block (i.e. ==== for an example block).

In the subsequent section Nesting blocks, it says:

When nesting a delimited block that uses the same structural container, it’s necessary to vary the length of the delimiter lines …

It does not say whether the extra characters used to alter the length can be arbitrary or must match the last specified character.

In other words, would ====xyz be valid as an example block delimiter or only ==== plus any number of = characters?

Working assumption

The extra characters must match the last character specified in the delimiter.