What I get from that is far more than 15% to 25% of all Muslims want Sahria law
As I've noted, a great many would like the family and civil end open to Muslims. The criminal portion is less enthusiastically and frequently supported and both are meant as options for Muslims, not those outside of the faith. Also, Muslims in the West and in places where there are democratic traditions have an appreciably decreased affinity for Sharia at all.
and from a related link that most Muslims believe suicide bombings are sometimes* justified (*"rarely/never"). That article confirmed and heightened my concerns, frankly.
"Muslims around the world strongly reject violence in the name of Islam. Asked specifically about suicide bombing, clear majorities in most countries say such acts are rarely or never justified as a means of defending Islam from its enemies."
Rarely and never were, unfortunately, made bedfellows in the inquiry.
Now given you seem concerned about a link between Sharia and violence, from the study:
Similarly, the survey finds no consistent link between support for enshrining sharia as official law and attitudes toward religiously motivated violence.
Also, the study noted that half of the Muslims in those countries were concerned about religious extremism. Most Muslims supported religious liberty and had a favorable view of democracy. In 31 of 38 predominantly Muslim countries Muslims said that other faiths were allowed to freely practice their religions and that they saw that freedom as a good thing.