ALG stands for application layer gateway and is an automatic function that will allow related traffic on ususally high ports that is related to the main traffic permitted by the policy. This describes the specific behavior of the MSRPC ALG.
A number of ALG are on by default on the SRX to permit common traffic. If you don't need the MSRPC ALG you can simply disable this ALG and the log messages will stop.
set security alg msrpc disable
If you are using MSRPC and need to correct for the traffic configure the specific traffic version needed here.