From GRFSpecs

Template for a small icon indicating support by TTDPatch or not.

No support {{ttdp|no}} Not supported by TTDPatch
Support, version unknown {{ttdp}} Supported by TTDPatch ????
⩾ 2.0 {{ttdp|2.0}} Supported by TTDPatch 2.02.0
⩾ 2.5 {{ttdp|2.5|2.0.1 alpha 3}} Supported by TTDPatch 2.5 (2.0.1 alpha 3)2.5
⩾ 2.6 {{ttdp|2.6|r2359}} Supported by TTDPatch 2.6 (r2359)2.6

Please only use version number of stable releases. You can put explicit revision numbers optionally in the second argument. It will only show in the hoover text of the image though. Also, never use the term "nightly", use the expected number of the next release for features which are not yet part of a stable release.

Note that the next stable release to "2.0.1 alpha xy" is actually "2.5".