First create a new column. Using the Formula in the column proporties of the new columnyou could use something like this, if you set your column first to a character column:
Num( Word( 1, :Name( "1500 meters" ), ":" ) ) * 60 + Num(Word( 2, :Name( "1500 meters" ), ":" ) + Num(Word( 3, :Name( "1500 meters" ), ":" )/100)
Or if you want to keep a numeric column with the h:m:s format you could create a new column using this formula:
Hour( :Name( "1500 meters" ) ) * 60 + Minute( :Name( "1500 meters" ) ) + Second( :Name( "1500 meters" ) ) / 100
The issue is that you will loose the fraction of seconds information, unless you set the number of decimal places to e.g. 10 and the input format as numeric and output to h:m:s. This is descripbed also with an example here: Discussions/Converting-numeric-seconds-to-0-00-0-time-format
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