Ah, it looks like you are trying to find something with hyphens inside the message field. The thing is the message field is an analyzed field (meaning it is stored for search optimization not as a string of text) you can read about it here Searching special characters - #7 by jan
The best way to solve this is to parse that value into its own field when its being ingested using a pipeline. Then it will be stored as a numeric value and you could run a search to find greater than etc.
But before you do all that, expand that message and see what fields other than the message field are available. There will be at least a few, and if it is a true syslog severity then it should already be in its own field.