Can I get Assets from a specific Matrix block?
You should be able to do this like so:

{% for block in entry.productIndo.type('specifications') %}
    {% for download in block.downloads %}
        {{ download.url }}
    {% endfor %}
{% endfor %}


Of if the nested loops don't suit you:

{% set specificationBlock = entry.productIndo.type('specifications').first() %}

{% if specificationBlock %}
    {% for download in block.specificationBlock %}
        {{ download.url }}
    {% endfor %}
{% endif %}