I need to know if the NetVanta 1550-24P can support 10GB SFPs in the four SFP slots
Yes.
Spec sheet here: https://portal.adtran.com/web/page/portal/Adtran/product/17101524F1/4495
Does that mean it can do 40GB when all four SFPs slots are populated with 10GB SFP's.
Data sheet lists a maximum forwarding bandwidth of 128 Gbps for the 1550-24 model and 176 Gbps for the 1550-48. So, yes.
https://portal.adtran.com/pub/Library/Data_Sheets/Default_Public/6171015xxF1-8%20NV1550%2024_48.pdf
Crunching the numbers, counting both ingress and egress, this specification adds up exactly to the sum of the wire speeds of all physical ports.
24 x 1Gbps x 2 (ingress and egress) = 48 Gbps
4 x 10Gbps x 2 (ingress and egress) = 80 Gbps
48 + 80 = 128. So it does wire speed on all ports.
Counting ingress and egress separately is kind of cheating in my opinion, like claiming that a T1 is 3Mbps because it's 1.5 in each direction. But I guess that's the way they all do it. Bottom line, according to the spec sheet it's wire speed on all interfaces.