I have used ambient at 1000% before now to light a room with Indirect Lighting with just playing about.
Yes Increasing ambient above 100 works.
If any off you reading this are wondering what Cog we are refering to then please read on. 
If you want to change the max or min value which in most cases will work.
Anyways if you haven’t noticed the little Cog next to the Values (See image one)
Clicking on the Cog will reveal a drop down box showing the command Parameter Settings. (See image two)
Another Window opens giving you the option of typing in new values and “Accept” applies the new values. (See image three)