This article goes into Miranda variants in some detail. The basic answer is that there are no SCOTUS-mandated formal requirements on the warning, and there exist up to 900 variants of the warning. The court only requires clear communication of those rights and appropriate waiver of them. The specific requirements, if any, are set by the jurisdiction. Since this is a constitutional issue, every jurisdiction must satisfy SCOTUS (and not the state's legislature). Some jurisdictions include a statement about providing a lawyer "if and when you go to court", which was found in Duckworth v. Eagan, 492 U.S. 195 to not render the warning inadequate (although it suggests that you only get a lawyer when you go to court). This gives rise to variants in New Jersey, Nevada, Oklahoma, and Alaska (but apparently not in Indiana where the warning originally arose).
The city of Seattle policy is stated here.
When advising a person of Miranda, officers will include the following
statements:
“You have the right to remain silent.”
“Anything you say can be used against you in a court of law.”
“You have the right at this time to talk to a lawyer and have your lawyer present with you while you are being questioned.”
“If you cannot afford to hire a lawyer, one will be appointed to represent you before questioning, if you wish.”
Officers will establish that the suspect understands in one of two
ways:
By asking “Do you understand” after each of the four Miranda warnings, or
By asking, “Do you understand each of these rights?” after reading all the warnings.
Officers may then begin asking questions.
If the arrestee makes a comment that causes the officer to believe
that the arrestee might be requesting an attorney, officers will ask
the arrestee to confirm, with a “yes” or “no” answer, whether the
arrestee is requesting an attorney.
There is no verbatim text that must be strictly adhered to, and the officer just has to "include the statements". The following section speaks of including an additional clause when "reading" Miranda to juveniles, but the previous section does not say that you have to literally read the warning from a card.
Analogously, pattern jury instructions are theoretically read verbatim from a script, and yet they are not (always?, ever?) transcribed into the record exactly as dictated by the jury instruction committee. In general, verbatim language is not legally required, especially in speech.
