As far as I know, that chart is only published here. I download the current value daily and graph it using a spreadsheet.

If you want to get the current number, though, I think you could normally find it on steemdb.io. As shown here.

For some reason, however, I notice that the main page on steemdb.io is showing data from July 31, so I'm not sure how often that gets updated. You could probably also pull it from the other block explorers, but I'm not sure exactly where.

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If you have a linux shell, here's a command you can use to get the number straight from the Steem API:

curl -s --data '{"jsonrpc":"2.0", "method":"condenser_api.get_dynamic_global_properties", "params":[], "id":1}' https://api.steemit.com | jq -rS .result.total_vesting_fund_steem | awk '{print $1}'