'eb patlh X means X%.

'eb patlh bID means 50/50 chance.

’eb patlh is literally "opportunity level" or "chance level," but, in this usage, it can be translated "risk level" or even just "chance" or "odds" (among other things).

The number is assumed to be a percentage (or as the numerator of a fraction whose denominator is 100) unless specified otherwise, so ’eb patlh 20 is sufficient, meaning "20 percent chance" or "risk level 20 (out of 100)." But you can always include the word vatlhvI' if you want.

When it’s not expressed as a percentage, the "risk level" is specified:

’eb patlh vagh loch wej
Risk level 3 out of 5.
3 out of 5 chance.

The 'eb patlh phrase is the object of bam "face" (that is, "have to deal with"), following a clause or another sentence that says what you’re talking about.

bIHeghmeH ’eb patlh 20 (vatlhvI’) Dabam.
You face a 20% chance of dying.
There is a 20% risk/chance of you dying.

chaq bIHegh. 'eb patlh vagh loch wa' Dabam.
Perhaps you will die. The odds are one out of five (that you will).

qurgh: The above sentence was originally given as wa' loch vagh but that means 5/1 and not 1/5 which is what the English says.