SGA_MAX_SIZE when AMM is enabled - 11.2.0;3 RAC DB

Hi

we have a 11.2.0.3 database (RAC) on Linux 5.x

we have AMM enabled .. i.e. MEMORY_TARGET and MEMORY_MAX_TARGET set

we performed the following...
alter system set sga_max_size=0 scope=spfile;

and bounced the database

but we are still seeing SGA_MAX_SIZE set to 2.6 GB


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
sga_max_size                         big integer 2656M
sga_target                           big integer 0
pga_aggregate_target                 big integer 0
memory_max_target                    big integer 7700M
memory_target                        big integer 6368M

why are we seeing this? Does this mean that SGA would only use a max of 2.6 GB although we have set the memory_max_target to 6.3 GB?