I have the following query
SELECT DISTINCT
HPNESTANC.ADNINGRES AS ESTANCIA1 , HPNESTANC.HESFECING AS FECHA_INGRESO FROM HPNESTANC
WHERE EXISTS
(SELECT MAX( HPNESTANC.ADNINGRES), MAX(HPNESTANC.HESFECING) FROM HPNESTANC WHERE HPNDEFCAM IN(80,237, 238,239,240,241,242,243,244,
245,247,248,249,245,247,248,249,250,251,252,253,254,255,256,257,256,357)
)ORDER BY 1
but I do not want to repeat those values in the result, the capture is the following: 
Assuming that the query that you currently have is correct, you only have to use it as an entry for another query that brings together and brings the maximum date.
Select ESTANCIA1, Max(FECHA_INGRESO)
from (tu select)
group by ESTANCIA1
You could not do a select is select, doing the following:
SELECT
HPNESTANC.ADNINGRES AS ESTANCIA1 , max(PNESTANC.HESFECING) AS FECHA_INGRESO FROM HPNESTANC
WHERE EXISTS
(SELECT MAX( HPNESTANC.ADNINGRES), MAX(HPNESTANC.HESFECING) FROM HPNESTANC WHERE HPNDEFCAM IN(80,237, 238,239,240,241,242,243,244,
245,247,248,249,245,247,248,249,250,251,252,253,254,255,256,257,256,357)
)
group by HPNESTANC.ADNINGRES
ORDER BY 1