Use case for this in core is the "Number of items to index during cron runs" setting in admin/config/search/settings:

It currently allows for a choice between 6 pre-defined values, as shown in the screenshot above. Ideally, we could allow any custom value (grater than 0), and offer these values as suggestions, instead of having them hard-coded.
The HTML5 number field allows that as follows:
<input id="ticketNum" type="number" name="ticketNum" list="defaultNumbers">
<span class="validity"></span>
<datalist id="defaultNumbers">
<option value="10045678">
<option value="103421">
<option value="11111111">
<option value="12345678">
<option value="12999922">
</datalist>
Which makes the <input> field a free-type number field + offers the suggested values in a drop-down in the same field:

Recent comments
well @herb I cannot believe it, but the webform module was there in modules on the disc, but missing in the listed modules, so I delete the module folder, and downloaded it again. Then...
My Webform Worksheets have disappeared
The only thing I can think of is to make sure Webform module is enabled and that the content type that needs to contain the webforms has Webform enabled for it. Edit the content type and make...
My Webform Worksheets have disappeared
@yorkshirepudding, In the end I fixed it by deleting the config/active folder contents, copying the config/staging/ files into config/active, importing the database again and clearing the caches...
Importing the staged config throws an error: another field with the same name already exists