Escalate On can be used for extending the escalation.

Select  Dynamic , then  configure Date and Time and then configure and then after and to be repeated.

For example, in this sceanrio:"I want the first mail is sent in 4 days, once you sent the first e-mail I want others to be sent daily"

Configure as below:

Date and Time : Activity Start Date + 3 days

and then after : 1 day

to be repeated: as applicable

Date and Time is configured as Activity StartDate + 3 Days because:

When selecting the option to extend the escalation by selecting and then after and/or to be repeated, the extension is added to the date and will only execute after the date has been reached AND the extension is complete. For example if you are using a Dynamic date of 1/1/2010 and select and then after to be 1 Day, the Escalation will only fire on the dynamically set date PLUS the and then after value which is 1/2/2010 in this case.

It is important to note that the Escalation will only fire on the dynamically set date PLUS the and then after value. It will NOT fire once on the dynamically set date and then again 1 Day after. It will only fire once

Reference: http://help.k2.com/onlinehelp/k2blackpearl/UserGuide/4.6.8/webframe.html#EscW06.html