Please answer a question about the following article about Aspirated consonant:

Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration ⟨◌˭⟩, a superscript equal sign: ⟨t˭⟩. Usually, however, unaspirated consonants are left unmarked: ⟨t⟩.

How are unaspirated or tenuis consonants sometimes marked for unaspiration?
with the modifier letter