regions, lines
<link rel="help" href="https://w3c.github.io/webvtt/#collect-webvtt-region-settings">

assert_equals(cues.length, 13);

var regions = Array.from(cues).map(function(cue) {
    return cue.region;
});

var valid_lines = [
    0,
    1,
    100,
    101,
    65536,
    4294967296,
    18446744073709552000,
    10000000000000000000000000000000000,
    2,
];
valid_lines.forEach(function(valid, index) {
    assert_equals(regions[index].lines, valid, 'Failed with region ' + index);
});

for (var i = 0; i < 4; i++) {
    var index = valid_lines.length + i;

    assert_equals(regions[index].lines, 3, 'Failed with region ' + index);
}

===
WEBVTT

NOTE valid

REGION
id:1
lines:0

REGION
id:2
lines:1

REGION
id:3
lines:100

REGION
id:4
lines:101

REGION
id:5
lines:65536

REGION
id:6
lines:4294967296

REGION
id:7
lines:18446744073709552000

REGION
id:8
lines:10000000000000000000000000000000000

REGION
id:9
lines:1 lines:3
lines:2

NOTE invalid

REGION
id:10
lines:-0

REGION
id:11
lines:1.5

REGION
id:12
lines:-1

REGION
id:13
lines: 1
lines :1

00:00:00.000 --> 00:00:01.000 region:1
text

00:00:00.000 --> 00:00:01.000 region:2
text

00:00:00.000 --> 00:00:01.000 region:3
text

00:00:00.000 --> 00:00:01.000 region:4
text

00:00:00.000 --> 00:00:01.000 region:5
text

00:00:00.000 --> 00:00:01.000 region:6
text

00:00:00.000 --> 00:00:01.000 region:7
text

00:00:00.000 --> 00:00:01.000 region:8
text

00:00:00.000 --> 00:00:01.000 region:9
text

00:00:00.000 --> 00:00:01.000 region:10
text

00:00:00.000 --> 00:00:01.000 region:11
text

00:00:00.000 --> 00:00:01.000 region:12
text

00:00:00.000 --> 00:00:01.000 region:13
text