[stumped]

when styles such as pcalibre get introduced by a conversion
why are they not shown in the expected alphabetic place i.e. next to other styles beginning with .p....

I was struggling to find one, which I could see in the book code, but not in the styles list...eventually i find it with a search - and it's not with the .p... CSS entries, but below the .X... entries

is there some subtle reason for that?
e.g. ( copied from sigil CSS list) note that the .pcalibre... styles come after all of the .x styles
.x13-bm-index2 {
display: block;
font-size: 0.7em;
margin-bottom: 0;
margin-left: 3.06em;
margin-right: 0;
margin-top: 0;
orphans: 2;
text-indent: -0.94em;
widows: 2
}
.pcalibre4:visited {
-webkit-text-fill-color: rgb(255, 102, 0);
color: rgb(255, 102, 0);
text-decoration: underline
}
.pcalibre6:link {
-webkit-text-fill-color: rgb(255, 102, 0);
color: rgb(255, 102, 0);
text-decoration: underline
}
.pcalibre1:first-letter {
color: #818180;
float: left;
font-size: 2.6em;
margin-bottom: 0;
margin-left: 0;
margin-right: 0.05em;
margin-top: 0
}
.pcalibre:first-letter {
color: #818180;
float: left;
font-size: 4em;
margin-bottom: 0;
margin-left: 0;
margin-right: 0.05em;
margin-top: 0
}