Ah, DBM. I was confused by the /count since DBM uses /pull. Same format, different function. Unfortunately, DBM doesn't expose its pull function, but we can use the registered SlashCmdList function instead.
Lua Code:
/run if SecureCmdOptionParse("[btn:2]") then SlashCmdList["DEADLYBOSSMODS"]("pull 3") else SlashCmdList["DEADLYBOSSMODS"]("pull 10") end