I select the add biometric button. The drop down list appears. I select systolic and the drop down box disappears. ??
After you choose the metric you want (i.e. systolic) you should be able to type in the value and log it to your diary. I'm not sure if that answers your question or explains what you're seeing. If you're still having a problem, some more details would be helpful -- for example, is this in the web or the mobile app?