Are you absolutely sure that he said 'short'? 'Short' does not make much sense in this context.
If you've taken this from a subtitle, it could be a mistake. The most likely word is SHARP, rather than 'short'. 'Sharp' - as in 'sharp-witted' - means astute or observant, and quick to notice and understand things. This makes perfect sense.
A sloppy and/or non-native subtitler, or voice recognition software, could easily mistake 'sharp' for 'short'. The realisation of the vowel may vary depending on the speaker's accent and the final consonant could easily be misheard. Remember that subtitles are very often wrong!