It means that it is available to order, from the factory.
And to even further manage expectations
@Moonlight... it doesn't even necessarily mean that. Plenty of TDs leave the label "in stock" on items that are no longer even made.
Whenever you want to order a rep, the most sensible process is:
1. Do some background research into the model you're interested in - which means reading on RWI (and elsewhere; other rep sites are available... although you should find what you're looking for here) and finding out what options are available right now.
2. Contact a TD (maybe contact a few - shipping prices and TD relationships with factories vary a little, so it can be beneficial to shop around) and ask whether they can get you the rep you're after.
3. Availability confirmed? Then make the payment.
4. Wait for the QC.
5. Get QC.
6. Don't post QC here, unless you have a specific concern about a particular possible flaw.
7. Approve QC.
8. Wait for the shipped rep.
9. Receive rep and do the Rep Received Happy Dance.
10. Post proud wristies on RWI.
Repeat, many times, as the Rep Obsession takes hold.