pack_input[ms]metric bigger than expected

[Rivon8]

I am running the cybersecurity example on a Pynq Z1 and a ZCU104 and it is slower than expected.
When I run
sudo python3.6 driver.py --exec_mode throughput_test --bitfile ../bitfile/finn-accel.bit --batchsize 1000
and then
cat nw_metrics.txt
I observed that the pack_input[ms] that it is a lot bigger than expected

pack_input[ms]: 78.14884185791016

When I try to test the example with different datasets the pack_input[ms] is even bigger.

What I am missing about the packing process?