Frida spawn Android app + hook native function

hook_native.py

import frida, sys

ss = """
Interceptor.attach(Module.findExportByName(null, "dlopen"), {
    onEnter: function (args) {
        this.path = Memory.readUtf8String(args[0]);
    },
    onLeave: function (retval) {
        if(!retval.isNull() && this.path.includes('libtest.so')) {
            var fstatat = resolveAddress('libtest.so', '0x0', '0x17FEB5');
            Interceptor.attach(fstatat, {
                onEnter: function (args) {
                    var p1 = Memory.readUtf8String(args[1]);
                    Memory.writeUtf8String(args[1], "/empty");
                },
                onLeave: function (retval) {
                }
            });
        }
    }
});
function resolveAddress(name, idaBase, idaAddr) {
    var baseAddr = Module.findBaseAddress(name);
    console.log('[+] BaseAddr of ' + name + ': ' + baseAddr);
      
    // Calculate offset in memory from base address in IDA database
    var offset = ptr(idaAddr).sub(idaBase);
      
    // Add current memory base address to offset of function to monitor
    var result = baseAddr.add(offset);
      
    // Write location of function in memory to console
    console.log('[+] Address in memory: ' + result);
    return result;
}
"""
device = frida.get_usb_device(timeout=1)
pid = device.spawn(["com.example.test"])
session = device.attach(pid)
script = session.create_script(ss)
script.load()
device.resume(pid)
sys.stdin.read()

please explain Calculate offset in memory from base address in IDA database ?