From NSIS Wiki
label_to_jump_to | +offset| -offset| user_var(target)
If label is specified, goto the label 'label_to_jump_to:'.
If +offset or -offset is specified, jump is relative by offset instructions. Goto +1 goes to the next instruction, Goto -1 goes to the previous instruction, etc.
If a user variable is specified, jumps to absolute address (generally you will want to get this value from a function like GetLabelAddress). Compiler flag commands and SectionIn aren't instructions so jumping over them has no effect.
Goto label Goto +2 Goto -2 Goto $0