ubu sam-xlate translate coordinates problem

[guanghaoli]

When I used sam-xlate to translate the genome coordinates to transcriptome coordinates, the bam file was much bigger. The genome coordinates bam is about 3gb, while the transcriptome coordinate bam is about 20gb. I used samtools flagstat to statistic the reads number and found that the reads number is about 20 times bigger. Could you please tell me why this problem occurs and how to deal with it?
genome bam flagstat:

transcriptome bam flagstat:

[mozack]

Reads that map to a single position can potentially map to mutiple transcripts. All possible transcript mappings are output.