Database

CREATE TABLE #MyTestBase (IDX INT, ExampleID INT, TestID INT);
INSERT INTO #MyTestBase (IDX, ExampleID, TestID) VALUES
(132326,406,NULL),(132358,513,NULL),(132367,513,NULL),(132373,513,NULL),(132374,406,NULL),
(132379,406,NULL),(132381,513,NULL),(132405,369,NULL),(132416,406,NULL),(132433,369,NULL),
(132438,369,NULL),(132444,406,NULL),(132457,369,NULL),(132461,406,NULL),(132465,369,NULL),
(132481,369,NULL),(132488,406,NULL),(132494,406,NULL),(132499,513,NULL),(132500,406,NULL),
(132507,406,NULL),(132520,513,NULL),(132521,369,NULL),(132525,369,NULL),(132533,406,NULL),
(132537,369,NULL),(132545,406,NULL),(132551,513,NULL),(132556,513,NULL),(132572,406,NULL),
(132580,369,NULL),(132593,329,NULL),(132600,513,NULL),(132629,513,NULL),(132695,513,NULL),
(132711,406,NULL),(132730,329,NULL),(132781,513,NULL),(132782,369,NULL),(132787,513,NULL),
(132800,406,NULL),(132805,369,NULL),(132813,513,NULL),(132831,369,NULL),(132842,406,NULL),
(132863,513,NULL),(132876,329,NULL),(132880,329,NULL),(132889,329,NULL),(132891,329,NULL),
(132908,329,NULL),(132913,406,NULL);

CREATE TABLE #MyTestCounts (TestID INT, CNT INT);
INSERT INTO #MyTestCounts (TestID, CNT) VALUES
(329,7),
(369,13),
(406,17),
(513,15);

SELECT * FROM #MyTestCounts;
SELECT * FROM #MyTestBase;

UPDATE Base
SET TestID = Counts.TestID
FROM #MyTestBase Base
CROSS APPLY #MyTestCounts Counts
WHERE ??? <= Counts.CNT
AND TestID IS NULL;