.block {
.block__2 {
...
}
}.block .block__2.block {
&__2 {
....
}
}.block__2
<percentage>
The percentage is calculated with respect to the width of the generated box's containing block. Note that this is true for 'margin-top' and 'margin-bottom' as well. If the containing block's width depends on this element, then the resulting layout is undefined in CSS 2.1.
Percentages: refer to logical width of containing block