Hi jmraimundo,
This is done on purpose to prevent performance issues that can occur when backloading larger dropdown menus in forms. You can adjust the value by editing the "MaxSelectList" variable in the web.cfg file. Again this is not something we recommend doing, but if you decide to do this, you would have to do it on all servers in the environment as well as make sure you do it to the web.cfg.tpl file (template) as well on each server so that it doesnt get overwritten when pdm configure is run.
Hope this helps,
Thanks,
Jon I.