DLA Piper law firm operates in 40+ countries and has 4,200 lawyers... They include more than half of the Fortune 250 and nearly half of the FTSE 350 or their subsidiaries.
People associated with DLA Piper also contributed to Jeb Bush, the RNC and the National Republican Senatorial Committee.
Gov Mike Castle and Fmr Senator Saxby Chambliss are partners in DLA Piper.
When they (Open Secrets and such) say it contributes this much to that politician, they are talking about everyone associated with that organization. The vast majority of the political contributions are from individuals and not necessarily from the DLA Piper law firm itself.