I'm sorry where can I see anything about this ''30 days rule''?
I checked all the links you quoted, couldn't find anything.
I have received some funds from MEXC in my personal wallet 60+ days ago and I'm really concerned what should I do now.
I believe this is what he's actually referring to:
Today’s action will protect the U.S. financial system from the significant illicit finance threats posed by MEXC Global. The order, issued pursuant to section 9714(a) of the Combating Russian Money Laundering Act, prohibits U.S. financial institutions from engaging in any transmittal of funds from or to MEXC Global. Violations of this order may result in civil or criminal penalties. The order does not modify existing obligations under the Bank Secrecy Act (including Suspicious Activity Report filing requirements) or sanctions administered by OFAC. The order is effective 30 days after publication in the Federal Register.
I could be wrong but exchanges starting to take action already is most likely because they cannot afford to leave this until the last minute?
Although, I don't believe that interacting with MEXC prior to that date (the 6th of November, or December) is going to change anything. Once an entity gets sanctioned, an exchange will automatically flag any incoming transaction from it whether the money came to the address 30 days ago, or five years ago.