Hi Bandar,
AC Power refers the main power in your country. E.g. 110v in US and 230v in UK. The T750 can be powered direct with AC power or with Power-over-Ethernet (PoE).
The reference to SFP+ Backhaul is referring to the use of the AP's SFP+ port - able to connect up to 10Gbps with an SFP fibre-optic module. In the case of the AP consuming 64.6 watts of power, this is when the AP is connected using an SFP fibre module, rather than just by the RJ45 ethernet port.
What the data sheet is illustrating is that when more of the APs hardware features are utilised, then it will consume more power when in operation.
I hope that helps,
Darrel.