Any specifier captalized means that they are optional and/or has a default value. Not sure if it's the smartest to have the first value as optional but your choice!
Right now your first string reads the whole params-string as you didn't set any length on it, meaning "d" (timer) and "s" (priezastis) will not really be read. Just guessing though, I might be wrong (especially about the S() reading the "d" part).