nginx – Is the output ts file size when using ffmpeg convert rtmp to hls with adaptive bitrate too large?

I want to convert rtmp to hls that supports adaptive bitrate , when referencing in many sources I use this configuration , but I found the ts file size of 240 to 720 bitrates is larger than I thought , I thought src will have to be the maximum size or 720p , please explain to me why , and is it possible to reduce the file size ( does any option in ffmpeg increase it ) ? Thanks everyone.

My ffmpeg command :

ffmpeg -i rtmp://localhost:1935/$app/$name -async 1 -vsync -1
                    -c:v libx264 -c:a aac -b:v 256k -b:a 64k -g 2 -vf "scale=426:trunc(ow/a/2)*2" -tune zerolatency -preset ultrafast -crf 23 -f flv rtmp://localhost:1935/show/$name_240
                    -c:v libx264 -c:a aac -b:v 768k -b:a 128k -g 2 -vf "scale=720:trunc(ow/a/2)*2" -tune zerolatency -preset ultrafast -crf 23 -f flv rtmp://localhost:1935/show/$name_360
                    -c:v libx264 -c:a aac -b:v 1024k -b:a 128k -g 2 -vf "scale=960:trunc(ow/a/2)*2" -tune zerolatency -preset ultrafast -crf 23 -f flv rtmp://localhost:1935/show/$name_480
                    -c:v libx264 -c:a aac -b:v 1920k -b:a 128k -g 2 -vf "scale=1280:trunc(ow/a/2)*2" -tune zerolatency -preset ultrafast -crf 23 -f flv rtmp://localhost:1935/show/$name_720
                    -c copy -f flv rtmp://localhost:1935/show/$name_src;

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