Hi Christian,
You mentioned mobile application, is the mobile application Agentry Mobile Apps?
If they are Agentry Mobile apps, you can find sizing guide in SAP service Marketplace.
Example: link to SAP Work Manager 6.3 sizing guide
Go to http://service.sap.com/instguides> Installation & Upgrade Guides > SAP Components > SAP Mobile -> SAP Work Manager -> SAP Work Manager 6.3
Chung