It depends.
A PR is a letter. A PR is for 6 months and is based on performance. A Warning Letter is typically behavior or action based and lasts 1 year. The kicker is that both are "active discipline" and count toward your 3 in a twelve month period.
You typically can not be issued a PR for something without an OLCC for the same issue first. If it's attendance, then the OLCC should state your current attendance/punctuality rating and as long as you remain above the minimum rating you would continue to receive OLCC for subsequent abscences/tardies. HOwever, if you fall below, then you should make a statement and would be issued a PR.
If the issue is something like lates just protect yourself. Tell the manager you will have lates and how many. Let the manager decide if balancing needs to happen or they can take the hit. Then by the time your station deems appropriate send a message to dispatch that you will have lates. This documents that you asked for help within a reasonable time. If you feel that you can not trust dispatch or management to tell the truth after you have protected yourself, then take a picture of the message you sent.
MFE has provided great advice. Put the onus on management to make the call. If you have poor scans (van, pup, pod) then you need to work on your methods and improve these skills. Take the extra time to verify scans. If you have equipment problems, then tell the gatekeeper and request that an OLCC compliment be put in the record.
Seriously, just WAD. and document it.