I was able to verify this for your data. I used space as the delimiter and under delimiter settings I enabled "Treat multiple delimiters as one". I also set the output type to Numerical Matrix. Here's what the generated script looks like. Feel free to explore the tool and add custom options to suit your needs.
%% Import data from text file
% Script for importing data from the following text file:
%
% filename: DATA.txt
%
% Auto-generated by MATLAB on 19-May-2021 15:08:15
%% Set up the Import Options and import the data
opts = delimitedTextImportOptions("NumVariables", 20);
% Specify range and delimiter
opts.DataLines = [16, 26];
opts.Delimiter = " ";
% Specify column names and types
opts.VariableNames = ["HCT", "Data", "Acquisition", "Version", "VarName5", ...
"VarName6", "VarName7", "VarName8", "VarName9", "VarName10", "VarName11", ...
"Var12", "Var13", "Var14", "Var15", "Var16", "Var17", "Var18", "Var19", "Var20"];
opts.SelectedVariableNames = ["HCT", "Data", "Acquisition", "Version", ...
"VarName5", "VarName6", "VarName7", "VarName8", "VarName9", "VarName10", "VarName11"];
opts.VariableTypes = ["double", "double", "double", "double", "double", ...
"double", "double", "double", "double", "double", "double", "string", ...
"string", "string", "string", "string", "string", "string", "string", "string"];
% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";
opts.ConsecutiveDelimitersRule = "join";
opts.LeadingDelimitersRule = "ignore";
% Specify variable properties
opts = setvaropts(opts, ["Var12", "Var13", "Var14", "Var15", "Var16", "Var17", ...
"Var18", "Var19", "Var20"], "WhitespaceRule", "preserve");
opts = setvaropts(opts, ["Var12", "Var13", "Var14", "Var15", "Var16", "Var17", ...
"Var18", "Var19", "Var20"], "EmptyFieldRule", "auto");
opts = setvaropts(opts, "HCT", "TrimNonNumeric", true);
opts = setvaropts(opts, "HCT", "ThousandsSeparator", ",");
% Import the data
DATA = readtable("DATA.txt", opts);
%% Convert to output type
DATA = table2array(DATA);
whos DATA
%% Clear temporary variables
clear opts
