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Initial Balance with FOREX

What is the best way to consider the initial balance in the FOREX market?

Could it be the whole asian session before London opens?

Could it be the first London session hour?

Should it be the first American session hour?

No books of market profile speaks about this issue

Thanks for any hint
Roughly the first 25% of each trading global session. This is the time major news comes out as well.

New York 8:00-10:00
Tokyo 19:00-21:00
London 3:00-5:00