Sharepoint Delay Activity is rounded off to the minute interval that is setup for ‘job-workflow’ property. This is because the job is responsible for waking up the workflow at the specified time. This job is usually set to run every 5 minutes.
It is easy to change (increase or decrease) this value.
To get the current job interval value:
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\BIN\stsadm -o getproperty -pn job-workflow -url http://siteaddress<
Or to change it every minute
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\BIN\stsadm -o setproperty -pn job-immediate-alerts -url http://siteaddress -pv "every 1 minutes between 0 and 59"
Just be careful about this on production server, as it would create extra load if set to 1 minute interval.