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Hi, I'm trying to find out what the parameters ng and m mean in the mos models of sky130. I believe they represent gate fingers and multipliers respectively, but I just can't be sure, and I can't find much info about it on the internet.

Edit: Additionally, I would also like to know the upper/lower limits on these parameters, if possible. A source that directs me to those parameters works as well.

it's pretty standard in SPICE models that "nf" is number of finger and "m" multiplicity, usually overall device width is "w*m" and finger width is "w/nf"

a sky130 mosfet has these parameters:

*`name=M3`*
*`L=0.5`*
*`W=1`*
*`nf=1 mult=1`*
`model=nfet_03v3_nvt`
`spiceprefix=X`

(The last two lines should in general not be changed).
W is the total width of the tranistor and nf is the number of  fingers the transistor is drawn on the layout. If W=10 and nf=2 there are 2 gates W=5 in parallel.

the m parameter multiplies everything by the specified number. It is the same as putting more devices in parallel, it is computationally efficient since the simulator modifies all calculated currents by the m factor, without evaluating more device equations.

Mosfet transistors also have drain and source areas and perimeters you can set manually if you want, AD, AS, PD, PS, and number of squares for source and drain diffusions, nrs and nrd. There are also SA, SB, SD  (*) parameters, these are set to 0.
Xschem calculates reasonable values for AD, AS, PD, PS, NRS, NRD from the W and L values, so you don't have to care about these. However you can manually override these for better parasitic R and C calculations.

I see. Are there any resources where I can read more about the parameters present in sky130 pdk and their limits? (for example, I think setting the multiplicity more than 100 gets you an error (108 in my case))

Usually ngspice tells you something like "model not found" if some transistor dimensions or parameters are out of allowed limits.
You can use this to check increasing parameters.
A more scientific approach is to dig into the model files and see the allowed ranges, for example for mosfets there is a `wmin`/`wmax` `lmin`/`lmax` set of parameters, among others.