#!/bin/bash


make_group_chapters()
{
    unset index i tmp
    input=( "$@" )
    chapters=()
    index=1

    chapters[$index]=${input[$((index-1))]}

    for ((i=1;i<${#input[@]};i++)); do
        tmp="${chapters[$index]##* }"
        if (( ${input[$i]%.*} > "${tmp%.*}" )); then
            chapters[$index]="${chapters[$index]} ${input[$i]}"
        else
            ((index++))
            chapters[$index]="${input[$i]}"
        fi
    done

    for c in ${!chapters[@]}; do
        chapter_array[x++]="${chapters[c]}"
    done
}

function format_seconds()
{
    awk '{
    hr=($1/3600); hd=(sprintf("%02d", hr))
    mr=((hr-hd)*60); md=(sprintf("%02d", mr))
    s=((mr-md)*60); sd=(sprintf("%02d", s))
    t=(sprintf("%02d:%02d:%06.3f" ,hd,md,s)); print t}' <<< $1
}


make_group_chapters "$@"

for index in "${!chapter_array[@]}"; do
    for number in ${chapter_array[index]}; do
        new_element="$new_element $(format_seconds $number)"
    done
    array[index]="$new_element"
    unset new_element
done

for i in ${!array[@]}; do
    echo "${array[i]}"
done

################################ output ###############################

$ sh work_on_numbers 30.345 52.234 66.32 12.34 42.52 73.34 26.34 4.34 60.34

 00:00:30.345 00:00:52.234 00:01:06.320
 00:00:12.340 00:00:42.520 00:01:13.340
 00:00:26.340
 00:00:04.340 00:01:00.340