SQL Server 2019

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CREATE TABLE yourTable (
    [FUND] varchar(255),
    [GRANT] varchar(255),
    [DATE] varchar(255),
    [POST] varchar(255),
    [WBS] varchar(255),
);

INSERT INTO yourTable
VALUES
('A', 'A', 'March 1, 2021', 10001, 'A'),
('A', 'A', 'March 1, 2021', 10001, 'B'),
('A', 'B', 'March 1, 2021', 10001, 'A'),
('B', 'A', 'March 1, 2021', 10001, 'A'),
('A', 'C', 'March 1, 2021', 10001, 'D'),
('B', 'A', 'April 1, 2021', 10001, 'A'),
('A', 'C', 'April 1, 2021', 10001, 'D'),
('A', 'A', 'March 1, 2021', 10002, 'A'),
('A', 'A', 'March 1, 2021', 10002, 'A'),
('B', 'A', 'March 1, 2021', 10002, 'A'),
('A', 'C', 'March 1, 2021', 10002, 'D'),
('A', 'A', 'March 1, 2021', 10002, 'A'),
('A', 'A', 'March 1, 2021', 10002, 'A'),
('A', 'A', 'April 1, 2021', 10002, 'A'),
('B', 'A', 'April 1, 2021', 10002, 'A'),
('A', 'C', 'April 1, 2021', 10002, 'D'),
('A', 'A', 'April 1, 2021', 10002, 'A');

WITH cte AS (
    SELECT *, DENSE_RANK() OVER (PARTITION BY DATE, POST
                                 ORDER BY FUND, [GRANT], WBS) dr
    FROM yourTable
)

SELECT POST, DATE, MAX(dr) AS COUNT
FROM cte
GROUP BY POST, DATE
ORDER BY POST, DATE;

POST	DATE	COUNT
10001	April 1, 2021	2
10001	March 1, 2021	5
10002	April 1, 2021	3
10002	March 1, 2021	3