Are you asking if the job is suspended whether it will resume from the same place it was up to?
If this is the case then it will depend on the agent type. For a basic windows file system, the job will resume from the file it was up to when the job was suspended. If you have a specific agent that you would like clarification on please let me know
Also if you are manually suspending and resuming the job you may wish to look at implementing an operation window for the client
Or throttling the bandwidth that the backup is using during business hours rather than suspending the job