Capital gains tax rates on taxable account

Hi all, I have a taxable account with $700k on a single fund (I know it’s dumb), and I want to diversify by exchanging a portion of it to international stocks and bonds. I bought the single fund over the course of the years since 2018. Approximately 72% of the shares were bought in the last year. The remaining more than 1 year ago. My question is: since capital gains are taxed as income if the share is held for less than 1 year, and at lower tax rate (15% for me) if held for more than 1 year, how would it be counted in my case? Like prorated as a full income for 72% and the rest taxed at 15%? Is it a reasonable assumption? I would wait one more year if 72% of the capital gains are fully taxed. Thanks everyone