For NPR Foreign Sourced income, is moving money from overseas to Japan considered first-in-first-out or last-in-first-out?

Sorry for the confusing title, not sure how I could word it. Numbers below are imaginary.

I want to move some of my savings to Japanese banks from overseas. I had a savings of $50,000 as of December 31, 2023. I earned $15,000 foreign source income so far in 2024 (ie dividends). So in total I have $65,000 right now.

If I move $20,000 to Japan now (May 2024), is that considered that I moved my savings, or did I move my foreign source income I earned in 2024? So essentially, am I not-taxable upto my savings amount ($50,000), or am I taxed from the first dollar I move?

Thank you

by len_anonymous