Why is chunkSize set in this way?

[luluzhou1]

Issue
In src/engine_multiexp.js line 127-137,

const opPromises = [];
        for (let i=0; i<nPoints; i += chunkSize) {
            if (logger) logger.debug(`Multiexp start: ${logText}: ${i}/${nPoints}`);
            const n= Math.min(nPoints - i, chunkSize);
            const buffBasesChunk = buffBases.slice(i*sGIn, (i+n)*sGIn);
            const buffScalarsChunk = buffScalars.slice(i*sScalar, (i+n)*sScalar);
            opPromises.push(_multiExpChunk(buffBasesChunk, buffScalarsChunk, inType, logger, logText).then( (r) => {
                if (logger) logger.debug(`Multiexp end: ${logText}: ${i}/${nPoints}`);
                return r;
            }));
        }

If I understand correctly, the purpose here is to execute the _multiExpChunk function in parallel. However, I cannot understand why chunkSize is set like this: chunkSize = Math.floor(nPoints / (tm.concurrency /nChunks)); (line 122).
For instance, in one proof generation where tm.concurrency = 10, nChunks = 18, and nPoints = 1020160, the resulting chunkSize is 1836288, which is greater than nPoints, leading to opPromises containing only one element.

Possible solution:
change line 122 to
chunkSize = Math.floor(nPoints / (tm.concurrency * nChunks));
After the change, the time spent on Multiexp has been reduced to approximately 80% of the original runtime.
I'm not entirely sure if this is the best solution, as I do not fully understand the meaning of nChunks. Any explanation of the meanings of pTSizes, bitChunkSize, and nChunks would be greatly appreciated.