If you have hundreds of builds doing it manually is not practical. You can use the rest api with curl, and your favorite scripting language
#!/bin/sh
project_id=456
token=secret
server=myserver
start_job=2
end_job=8
for job_id in $(seq $start_job $end_job)
do
curl --request POST --header "PRIVATE-TOKEN:${token}" "https://${server}/api/v4/projects/${project_id}/jobs/${job_id}/erase"
done