RSSI numbers

I jus brought a chime pro and need help figuring out the signal strength and what the RSSI numbers mean. I have a front & back door bell 4 cam and the RSSI are -60 and -49 both connected to my WiFi. I have 2 spotlight cams and the RSSI numbers r -60 using WiFi & -62 using the chime connection. The other is -73 using WiFi and -65 using chime connection. The chime itself has RSSI number of -39. I put the chime plug bout 3 feet from the router. My 2 doorbells & 1 of the spot light cam which I installed on diff days was working fine, but when I put the other up, things we're getting slow and not connecting. Can someone tell me what the RSSI numbers r far as being good or bad and what can I do to improve them?