How to pool scores of experimental group to compare with control to calculate Hedges d?

I am doing a meta-analysis and trying to compute Hedge's g from statistics reported in each study. In one paper, the experimental group (N=18) were assessed on 4 variables (vocab, comprehension, pronunciation, listening). I have the M and SD for each of these variables.

I would like to combine these 4 of these variables in the experimental group into one using the pool.groups in dmetar package in R so I can compare that with the control group to get Hedges d overall effect. I am not sure how to compute it meaningfully as the same # of participants did all 4 variables above (vocab, comprehension...), so the sample size line in the code won't be correct as it's not different groups of people but within-groups. Can someone advise if they have any ideas how to do this meaningfully?

Here is how the function worked with another study, in which the N were actually 2 different experimental groups

library(dmetar)
pool.groups(n1=35,
n2=35,
m1=68.28,
m2=74.74,
sd1=8.47,
sd2=8.68)
result: Mpooled value, SD pooled value, Npooled value

All advice is appreciated. Thanks in advance

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