Why is the frame around the Grid not displaying correctly?

H

HitGirl2020-04-16 21:06:44

css

HitGirl, 2020-04-16 21:06:44

Hello!
Can you please tell me why the frame around the grida is wider and smaller in height than the grid itself?

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="style.css">
    <title>Document</title>
</head>
<body>
<div class="container">
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item-b"></div>
</div>
</body>

*{
    margin: 0;
    padding: 0;
}
.container {
    gap: 15px 16px;
    display: grid;
    border: 1px solid black;
    grid-template-columns:  40px  50px  40px 50px  40px ;
    grid-template-rows: 25% 100px 30px;
}
.item{
    background-color: #F00;
}
.item-b {
    background-color: #00F;
    grid-column-start: 1;
    grid-column-end: span 4;
    grid-row-start: 2;
    grid-row-end: 4;
}