For some mutual funds, the “Daily dividend accrual” value is the portion of the upcoming dividend that has accrued up to the evaluation date, times the number of shares. If the previous dividend paid on, say, the 15th of the month and the evaluation date is the 20th of the month, then five days of the new dividend have accrued. Sum these daily values and multiply by the shares, and that’s the daily dividend accrual.
The daily values themselves are produced by the fund vendors, and can vary day-to-day depending on the holdings of the fund for any particular day, though when you sum all of them for the month, they will equal the value of the dividend that’s ultimately issued.