https://jsfiddle.net/t5upngoo/6/

<div class="amount-select">
  <div>50</div>
  <div>100</div>
  <div>200</div>
  <div>300</div>
  <div>500</div>
  <div></div>
</div>

*{
  padding:0;
  margin:0;
  box-sizing:border-box;
}
.amount-select {
  display: flex;
  margin-right: -3%;
  flex-wrap: wrap;
  width: 100%;
}

.amount-select>div {
  width: 20%;
  height: 100px;
  text-align: center;
  color: -sharp13b7f6;
  border: 1px solid -sharp13b7f6;
  margin-right: 3%;
  margin-bottom: 20px;
}

is divided into two row,. The upper line justifyContent is set to center, and the lower line is set to flex-start. The following line needs to set marginLeft