If you attach an external keyboard to an Apple iPad and open analysis an containing dropdown property control in the TIBCO Spotfire for Apple iOS application, you will notice that it only filters the values based on the first typed letter. When trying to reproduce the same behavior on TIBCO Spotfire Analyst client on Windows/Mac desktop, this behavior is not seen and it will instead filter based on all typed characters.

For example:
Suppose, your dropdown list contains world country names. Now, if you press "can" letters on keyboard, it will show the following list:

If you type "mala" on keyboard, it will show the following list:

Alternatively, on a mobile Apple device with an external keyboard attached, on typing "can" or "mala", it will fetch all the values containing "c" or "m" respectively.

This article explains the difference in behavior in the dropdown list on Ipad

This difference in behavior between touch and non-touch devices is as designed.

The dropdown list implementation is done differently for touch devices. On non-touch devices, the list implementation is customized. On touch devices, the standard controls have been used for list implementation as they provide a better touch experience. An effect of this is that the behavior will be different when attaching an external keyboard to touch devices.

Doc: TIBCO Spotfire for Apple IOS

• https://docs.tibco.com/pub/sf_ipad/2.11.1/doc/html/en-US/GUID-4A613825-2558-481D-9F0A-A696D88C3EB7.html