Meta objective and cost results slight difference

[ArthurduVignau]

In different cost optimizations I have found that the result displayed via printCosts and printMetaResults have a slight diffrence.
In the different optimizations ran, it do not always occcurs but does most of the time. I am working with 3 buildings (B1,B2,B3). Here is the list of optim I have done :

building(s) : MIPGap/MIPFocus, bug presence (yes/no), % of difference between cost and objective (objective always bigger)

optim with one buildings :
B1 : E-1/3 no, E-3/2 yes 0.7%
B2 : E-1/3 no, E-3/2 no
B3 : E-1/3 no, E-3/2 no

optim with the three buildings :
B1B2B3 :

Group E-2/2 All links annual yes 0.3%
Group E-2/2 All links january yes 1.8%

Indiv E-1/3 yes 0.3%
Indiv E-3/2 yes 0.1%

Indiv Merged=True E-3/2 January yes 4.6%