Why is the yield and SEC 30 day yield of TLT so different? Which one tells you the annualized rate of the next dividend?

On yahoo, it says the yield is 3.57%

https://finance.yahoo.com/quote/TLT/

On the ishares website, it says the yield is 4.57%

https://www.ishares.com/us/products/239454/ishares-20-year-treasury-bond-etf

Lastly let's say the next dividend is going to be 4.71% annualized, if TLT drops in price but i already own shares before the drop, will the 4.71% number go up or down or stay the same?