How to clear staging task table?

Out of 12 GB of database size, 10 GB is consumed by Staging_Task table.

I need to understand, what causes this table to grow like this. What should I do to limit this? How can I clear it?

I got this script on devnet but looks like it is for the older versions.

BEGIN TRANSACTION
BEGIN TRY

ALTER TABLE [dbo].[Staging_SyncLog] DROP CONSTRAINT [FK_Staging_SyncLog_SyncLogTaskID_Staging_Task]
ALTER TABLE [dbo].[Staging_Synchronization] DROP CONSTRAINT [FK_Staging_Synchronization_SynchronizationTaskID_Staging_Task]


truncate table staging_synchronization
truncate table staging_synclog
truncate table staging_task

ALTER TABLE [dbo].[Staging_SyncLog]  WITH CHECK ADD  CONSTRAINT [FK_Staging_SyncLog_SyncLogTaskID_Staging_Task] FOREIGN KEY([SyncLogTaskID])
REFERENCES [dbo].[Staging_Task] ([TaskID])
ALTER TABLE [dbo].[Staging_SyncLog] CHECK CONSTRAINT [FK_Staging_SyncLog_SyncLogTaskID_Staging_Task]

ALTER TABLE [dbo].[Staging_Synchronization]  WITH CHECK ADD  CONSTRAINT [FK_Staging_Synchronization_SynchronizationTaskID_Staging_Task] FOREIGN KEY([SynchronizationTaskID])
REFERENCES [dbo].[Staging_Task] ([TaskID])
ALTER TABLE [dbo].[Staging_Synchronization] CHECK CONSTRAINT [FK_Staging_Synchronization_SynchronizationTaskID_Staging_Task]

END TRY
BEGIN CATCH

IF @@TRANCOUNT > 0
    ROLLBACK TRANSACTION;

DECLARE @ErrorMessage NVARCHAR(4000), @ErrorSeverity INT, @ErrorState INT;

SELECT @ErrorMessage = ERROR_MESSAGE(),
        @ErrorSeverity = ERROR_SEVERITY(),
        @ErrorState = ERROR_STATE();

RAISERROR (@ErrorMessage, @ErrorSeverity, @ErrorState);
END CATCH   


IF @@TRANCOUNT > 0
COMMIT TRANSACTION;

Does it grow because somebody has checked out pages and didn't checked in. Please help, thanks