calculate monthly average for each column based on the last recorded timestamp for each day Sql server

select [SName],MAX([DateTime]) as Dates

    from table

where [DateTime] between @MNT1 and @MXT1  and [DateTime] <=@MXT1 

    group by[SName] ,CONVERT(Date,[DateTime])
    order by [SName],CONVERT(Date,[DateTime])

I'd like to somehow calculate average only for the max timestamp per day for each column.
@mnt1 and 2 are set as start date and end date for report

ID SERVERNAME COL2 COL3 COLN DATETIME
1   A          1.1  1.5      2022-08-01 23:50:13.0000000
2   A          1.1  1.6      2022-08-01 23:55:13.55530000
3   B          1.7  2        2022-08-01 23:50:13.7530000
4   C          3.4  2        2022-08-02 23:50:13.7530000
5   C          1.4  5        2022-08-08 23:50:13.7530000

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I'm trying to calculate average based on the last value logged per day for each server eg. server A for month of august will have timestamps throughout the day till server is shut down at midnight ,for A il have last recorded date timestamp for the 1st of august through to end of august now I need to capture those and calculate monthly average soley based on those timestamps and so on foe each server