Changing the buffer size and count in the agent will not resolve your skipped purepath issue. Reducing buffer size and count will only cause more issues, it should be left at the default values unless told otherwise by Dynatrace support team during the resolution of a support ticket.
Skipped purepaths are more likely caused by a misconfigured AppMon Server. I would inspect the Deployment Health dashboards. These are available from the left cockpit under "Deployment Health". Start with the "Server Health" dashboard. CPU Being overdriven? Queue Saturation? Memory overutilized?
If nothing is obviously wrong, a support case might be necessary to help interpret the root cause of skipped PPs.
What will be the default value for Buffer Count and Size?
We have a support case as well SUPDT-44346 for the same. Seems it's like never solved case. We have doubled the number of collectors we have earlier but still we are seeing skipped PP's.
Sree, Can you confirm which version of AppMon you're using. You selected 7.0 as a tag for this posting, but as I recall, the buffer sizes and counts were hidden in v7, and no longer user editable.
To determine your default values, based on which version you have, possibly just create a new Agent Mapping and examine the default values created for this new Mapping entity.