4 percent rate to balances less than or equal to $1,500;
5 percent to balances above $1,500, but less than or equal to $2,500; and
6 percent to balances above $2,500.

Under tiering method B for a balance of $4,000, would the customer earn 6 % on $1,500 (4,000 - 2,500) and 5% on 1,500 (min bal on tier 2) and 4% on the remaining $1,000 (lowest tier)?

In a manual I am reading they say he would get 6% on $1,500, 5% on $1,000, and 4% on $1,500. I can't figure out how they came up with balances on which to pay.

The example in your manual seems correct to me (apart from rounding for amounts over... i.e 1500.01 to 2,500).

The first tier (4%) is 0.01 to 1,500 = 1500
The second tier (5%) is 1500.01 to 2500 = 1000
The third tier (6%) is 2500 to 4000 = 1500

There is an example in Appendix A to Reg DD that might also be useful: https://www.bankersonline.com/regulations/12-1030-appa

Thank you Adam. I had myself so confused, but the light bulb finally went off

Which will result in having to advertise a range of APYs for other than the first tier.

If the min bal to earn interest is $500. Does the bank disclose the first tier as:

If your daily balance is $500 or less, the interest rate paid on the entire balance will be 0% with an annual percentage yield of 0% OR

If your daily balance is greater than $500 but less than $1,500, the interest rate paid on the entire balance will be 4% with an annual percentage yield of xx%