table {width: 350px;}
table, td {border: 1px solid black;}
.first {width: 30px;}
.ex1 {
table-layout: auto;
}
.ex2 {
table-layout: fixed;
}
<!DOCTYPE html>
<html lang="ko">
<head></head>
<body>
<p>table-layout: auto:</p>
<table class="ex1">
<tr>
<td class="first">1000000000000000000000000000</td>
<td>10000000</td>
</tr>
</table>
<p>table-layout: fixed:</p>
<table class="ex2">
<tr>
<td class="first">1000000000000000000000000000</td>
<td>10000000</td>
</tr>
</table>
</body>
</html>