You can do it in sed, yes. Just search for 60 Secs ( and then as many non-% characters as possible until the first %:
$ echo "5 Secs (11.2345%) 60 Secs (22.3456%) 300 Secs (33.4567%)" |
sed 's/.* 60 Secs (\([^%]*%\).*/\1/'
22.3456%
Or, in perl:
$ echo "5 Secs (11.2345%) 60 Secs (22.3456%) 300 Secs (33.4567%)" |
perl -lne '/.* 60 Secs \(([^%]*%)/; print "$1"'
22.3456%
Or, if the format is standard and you know you always want the 6th field, you can do:
$ echo "5 Secs (11.2345%) 60 Secs (22.3456%) 300 Secs (33.4567%)" |
awk '{gsub(/[()]/,""); print $6}'
22.3456%
or:
$ echo "5 Secs (11.2345%) 60 Secs (22.3456%) 300 Secs (33.4567%)" |
cut -d' ' -f6 | tr -d '()'
22.3456%
()after5 Secs.