Permitted composition of lithium oxometallate in lithium-ion battery and its influence on ion transfer

The following scheme describes the overall reaction that takes place in a Li-ion battery:


$$
\begin{align}
\ce{Li\_{$y$}C6 &-> $y$ Li+ + $y$ e- + C6} &\quad &\text{(anode)} \tag{R1}\\
\ce{Li\_{$1-y$}MO2 + $y$ Li+ + $y$ e- &-> LiMO2} &\quad &\text{(cathode)} \tag{R2}\\
\hline
\ce{Li\_{$y$}C6 + Li\_{$1-y$}MO2 &-> LiMO2 + C6} \tag{R3}
\end{align}
$$


However, I'm confused by the $1-y$ subscript in the lithium oxometallate. While the formula makes sense for $y=1$ $(1 - 1 = 0),$ if $y=2,$ wouldn't the subscript for $\ce{Li}$ be negative?


What would this physically correspond to in terms of lithium ion transfer?


