Yes it is. Write %c in the text field instead and put this function into the text editor:
123 will still display as 123
local name,_,icon,_,_,_,_,_,_,_,_,_,_,_,value=UnitBuff("player", "Ignite")
if(value > 999999) then value = math.floor(value/1000000) .. "M" end
if(value > 999) then value = math.floor(value/1000) .. "k" end
12345 will display as 12k
1234567 will display as 1M, which might not be of much interest when it comes to ignite but perhaps usable for other buffs.