The Royal Match SB is a very difficult proposition to bet advantageously. It has no correlation to a typical count system. For further info you should refer to Snyder's Big Book of BJ.
I strongly advise NOT to bet it!
The only version of RM that has any viability is the 1D 3/10 payoff version like Cortez features. The housEdge for 1D 3/10 version is 3.5% and unlike other SB schemes it never goes higher, but it does go lower and occaisionally favors the player.
In a nutshell there are a few convergent approaches:
1. When there is an excess of one suit depleted
2. When there is an overabundance of one suit remaining
3. When there is an excess of one color (red/black) depleted
4. When there is an excess of suited Ks/Qs remaining and one of the previous factors is apparent.
One simple count (again, NOT RECOMMENDED) is to count red cards +1 and black cards -1... whenever the RM RC is +7 (or higher) or -7 (or lower) you may place the RM bet.
Don't do it! zg
Ps - A much more beatable SB is the LLadies and its cousin the Royal20s (last seen only at Plaza). These SBs do correlate to the standard count - see previous posts this forum.