Attribution windows typically apply to an email or ad that makes a single impression - Opensend is different, because Opensend identifies quality leads for you that can, and should, nurture on an ongoing basis.
Therefore, Opensend doesn't have a set attribution window. Leads identified by Opensend can convert after retargeting and nurturing from any number email flows or ad campaigns, and the attribution for those flows/campaigns is measured within your email marketing and/or Facebook/Google platforms.
While some leads may convert in the short term off a welcome or abandonment flow, others may need more nurturing and can convert down the road. Many will turn into repeat customers. The Placed Order Value that you see on the Opensend dashboard, when integrating with a supported Email platform, includes all orders placed by Opensend-identified profiles - throughout their marketing journey - within the selected date range. For more insight on the performance of individual flows or campaigns, visit your email and ad platforms.