Hi. Very new rider gaining experience in an eBay special before hopefully buying a proper bike.

Replaced an inner tube on the back and noticed that the wheel doesn't settle correctly on the dropouts as I expected them to. Should they fit in exactly? Haven't ridden since as concerned wheel isn't on securely. Friend has mentioned that the wheel is a bit off centre but at my stage it isn't that important. I have attached a photo. Could someone please let me know if the dropouts are for adjustment or the wheel is unsafe. Thank you for any replies